Vulnerability-Lookup

CVE-2026-45681 (GCVE-0-2026-45681)

Vulnerability from cvelistv5 – Published: 2026-06-02 15:25 – Updated: 2026-06-02 18:05

Title

OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size

Summary

OpenTelemetry eBPF Instrumentation provides eBPF instrumentation based on the OpenTelemetry standard. Prior to version 0.9.0, the per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry. This issue has been patched in version 0.9.0.

Severity

5.9 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-125 - Out-of-bounds Read
CWE-130 - Improper Handling of Length Parameter Inconsistency

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/open-telemetry/opentelemetry-e…	x_refsource_CONFIRM
https://github.com/open-telemetry/opentelemetry-e…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
open-telemetry	opentelemetry-ebpf-instrumentation	Affected: < 0.9.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-45681",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-02T18:05:10.631730Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-02T18:05:14.202Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "opentelemetry-ebpf-instrumentation",
          "vendor": "open-telemetry",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.9.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "OpenTelemetry eBPF Instrumentation provides eBPF instrumentation based on the OpenTelemetry standard. Prior to version 0.9.0, the per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry. This issue has been patched in version 0.9.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-125",
              "description": "CWE-125: Out-of-bounds Read",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-130",
              "description": "CWE-130: Improper Handling of Length Parameter Inconsistency",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-02T15:25:00.260Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9"
        },
        {
          "name": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0"
        }
      ],
      "source": {
        "advisory": "GHSA-r6c9-g6q5-qrf9",
        "discovery": "UNKNOWN"
      },
      "title": "OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-45681",
    "datePublished": "2026-06-02T15:25:00.260Z",
    "dateReserved": "2026-05-12T21:59:25.667Z",
    "dateUpdated": "2026-06-02T18:05:14.202Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-45681",
      "date": "2026-07-22",
      "epss": "0.00287",
      "percentile": "0.20846"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-45681\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-06-02T16:16:42.753\",\"lastModified\":\"2026-07-22T19:10:00.120\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"OpenTelemetry eBPF Instrumentation provides eBPF instrumentation based on the OpenTelemetry standard. Prior to version 0.9.0, the per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry. This issue has been patched in version 0.9.0.\"},{\"lang\":\"es\",\"value\":\"La Instrumentaci\u00f3n OpenTelemetry eBPF proporciona instrumentaci\u00f3n eBPF basada en el est\u00e1ndar OpenTelemetry. Antes de la versi\u00f3n 0.9.0, la ruta de respaldo del b\u00fafer de mensajes por CPU utiliza un b\u00fafer de respaldo de 256 bytes pero conserva el tama\u00f1o original de la carga \u00fatil, que puede ser de hasta 8KB. Si se produce una discrepancia de CPU, OBI puede leer m\u00e1s all\u00e1 del b\u00fafer de respaldo y filtrar memoria adyacente en la telemetr\u00eda. Este problema ha sido parcheado en la versi\u00f3n 0.9.0.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"open-telemetry\",\"product\":\"opentelemetry-ebpf-instrumentation\",\"versions\":[{\"version\":\"\u003c 0.9.0\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N\",\"baseScore\":5.9,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.2,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-06-02T18:05:10.631730Z\",\"id\":\"CVE-2026-45681\",\"options\":[{\"exploitation\":\"poc\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-125\"},{\"lang\":\"en\",\"value\":\"CWE-130\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:opentelemetry:ebpf_instrumentation:*:*:*:*:*:go:*:*\",\"versionEndExcluding\":\"0.9.0\",\"matchCriteriaId\":\"72CC55EE-4DFB-417E-B148-642944DFC24F\"}]}]}],\"references\":[{\"url\":\"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Product\",\"Release Notes\"]},{\"url\":\"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]},{\"url\":\"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9\",\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "current_release_date": "2026-06-05T19:32:54+00:00",
      "cve": "CVE-2026-45681",
      "id": "CVE-2026-45681",
      "initial_release_date": "2026-01-01T00:00:00+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45681.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-06-04T02:23:04Z",
      "cve": "CVE-2026-45681",
      "id": "CVE-2026-45681",
      "initial_release_date": "2026-06-04T02:23:04Z",
      "product_status:known_affected": "8",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-45681",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-45681.json",
      "version": "2"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-45681\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-02T18:05:10.631730Z\"}}}], \"references\": [{\"url\": \"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-02T18:05:02.972Z\"}}], \"cna\": {\"title\": \"OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size\", \"source\": {\"advisory\": \"GHSA-r6c9-g6q5-qrf9\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 5.9, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"HIGH\"}}], \"affected\": [{\"vendor\": \"open-telemetry\", \"product\": \"opentelemetry-ebpf-instrumentation\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 0.9.0\"}]}], \"references\": [{\"url\": \"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9\", \"name\": \"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0\", \"name\": \"https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"OpenTelemetry eBPF Instrumentation provides eBPF instrumentation based on the OpenTelemetry standard. Prior to version 0.9.0, the per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry. This issue has been patched in version 0.9.0.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-125\", \"description\": \"CWE-125: Out-of-bounds Read\"}]}, {\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-130\", \"description\": \"CWE-130: Improper Handling of Length Parameter Inconsistency\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-06-02T15:25:00.260Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-45681\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-02T18:05:14.202Z\", \"dateReserved\": \"2026-05-12T21:59:25.667Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-06-02T15:25:00.260Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2026-45681

Vulnerability from fkie_nvd - Published: 2026-06-02 16:16 - Updated: 2026-07-22 19:10

Severity

5.9 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0	Product, Release Notes
security-advisories@github.com	https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9	Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	opentelemetry	ebpf_instrumentation	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "opentelemetry-ebpf-instrumentation",
          "vendor": "open-telemetry",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.9.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:opentelemetry:ebpf_instrumentation:*:*:*:*:*:go:*:*",
              "matchCriteriaId": "72CC55EE-4DFB-417E-B148-642944DFC24F",
              "versionEndExcluding": "0.9.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "OpenTelemetry eBPF Instrumentation provides eBPF instrumentation based on the OpenTelemetry standard. Prior to version 0.9.0, the per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry. This issue has been patched in version 0.9.0."
    },
    {
      "lang": "es",
      "value": "La Instrumentaci\u00f3n OpenTelemetry eBPF proporciona instrumentaci\u00f3n eBPF basada en el est\u00e1ndar OpenTelemetry. Antes de la versi\u00f3n 0.9.0, la ruta de respaldo del b\u00fafer de mensajes por CPU utiliza un b\u00fafer de respaldo de 256 bytes pero conserva el tama\u00f1o original de la carga \u00fatil, que puede ser de hasta 8KB. Si se produce una discrepancia de CPU, OBI puede leer m\u00e1s all\u00e1 del b\u00fafer de respaldo y filtrar memoria adyacente en la telemetr\u00eda. Este problema ha sido parcheado en la versi\u00f3n 0.9.0."
    }
  ],
  "id": "CVE-2026-45681",
  "lastModified": "2026-07-22T19:10:00.120",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-45681",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-02T18:05:10.631730Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-02T16:16:42.753",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Product",
        "Release Notes"
      ],
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        },
        {
          "lang": "en",
          "value": "CWE-130"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-R6C9-G6Q5-QRF9

Vulnerability from github – Published: 2026-05-18 20:11 – Updated: 2026-06-09 10:58

Summary

OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size

Details

Summary

The per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry.

Details

https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/common/http_buf_size.h#L4-L7

k_kprobes_http2_buf_size is defined as 256 bytes, the size of the fallback buffer.

https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/common/msg_buffer.h#L12-L36

Introduces 8KB per-CPU buffer and 256-byte fallback_buf in msg_buffer_t, creating a size mismatch for fallback use.

https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/generictracer/k_tracer.c#L370-L394

On CPU mismatch, fallback_bufis used but size is still set to m_buf->real_size (up to 8KB) and passed downstream.

https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/generictracer/protocol_http.h#L412-L441

bytes_len (from m_buf->real_size) is used to read payload data from u_buf; if u_buf is the 256B fallback, this can over-read and leak memory into telemetry.

https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/tpinjector/tpinjector.c#L192-L206

real_sizeis set up to 8192 bytes and stored with cpu_id; fallback_bufonly contains 256 bytes.

PoC

Local testing with an AddressSanitizer user-space PoC reproduced the same class of size-mismatch over-read as the vulnerable fallback-buffer path. That result is sufficient to ground the advisory in a fresh local reproduction even though the exact end-to-end eBPF path still depends on host BPF capabilities.

To reproduce the validated behavior locally:

create a struct that models fallback_buf[256] and real_size
populate only the 256-byte fallback buffer
simulate the CPU mismatch path by using the fallback buffer as the source pointer while preserving a much larger real_size
perform a read of real_size bytes from that 256-byte backing store under ASan

An equivalent reproducer is:

// save as /tmp/poc_msgbuf_oob.c
#include <stdint.h>
#include <stdio.h>
#include <string.h>

struct msg_buffer {
  unsigned char fallback_buf[256];
  uint16_t pos;
  uint16_t real_size;
  uint32_t cpu_id;
};

int main(void) {
  struct msg_buffer m = {0};
  unsigned char sink[8192];

  memset(m.fallback_buf, 'A', sizeof(m.fallback_buf));
  m.real_size = 4096;

  memcpy(sink, m.fallback_buf, m.real_size);
  printf("copied %u bytes from a 256-byte fallback buffer\n", m.real_size);
  return 0;
}

Compile and run with ASan:

cc -fsanitize=address -O1 -g -o /tmp/poc_msgbuf_oob /tmp/poc_msgbuf_oob.c
ASAN_OPTIONS=abort_on_error=1 /tmp/poc_msgbuf_oob

Expected result:

AddressSanitizer: heap-buffer-overflow or stack-buffer-overflow

That user-space PoC matches the size-mismatch condition in the vulnerable code path, even though the exact end-to-end eBPF runtime path still requires host BPF attach/load capability.

Impact

This is a confidentiality issue in the HTTP tracing path. The vulnerable read occurs in OBI's local fallback-buffer handling when context propagation is enabled, the tpinjector sock_msg path is active, HTTP large-buffer capture is configured with a non-zero size, and a CPU mismatch occurs between producer and consumer contexts. Under those conditions, OBI can over-read from the fallback buffer and export unrelated memory through telemetry.

Severity

5.9 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "go.opentelemetry.io/obi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45681"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125",
      "CWE-130"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-18T20:11:20Z",
    "nvd_published_at": "2026-06-02T16:16:42Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe per-CPU message-buffer fallback path uses a 256-byte backup buffer but preserves the original payload size, which can be up to 8KB. If a CPU mismatch occurs, OBI can read beyond the fallback buffer and leak adjacent memory into telemetry.\n\n### Details\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/common/http_buf_size.h#L4-L7\n\n`k_kprobes_http2_buf_size` is defined as 256 bytes, the size of the fallback buffer.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/common/msg_buffer.h#L12-L36\n\nIntroduces 8KB per-CPU buffer and 256-byte `fallback_buf` in `msg_buffer_t`, creating a size mismatch for fallback use.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/generictracer/k_tracer.c#L370-L394\n\nOn CPU mismatch, `fallback_buf `is used but size is still set to `m_buf-\u003ereal_size` (up to 8KB) and passed downstream.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/generictracer/protocol_http.h#L412-L441\n\n`bytes_len (from m_buf-\u003ereal_size)` is used to read payload data from `u_buf`; if `u_buf` is the 256B fallback, this can over-read and leak memory into telemetry.\n\nhttps://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/blob/032473449b53d9f02ec4619d4f5b84e6a81db362/bpf/tpinjector/tpinjector.c#L192-L206\n\n`real_size `is set up to 8192 bytes and stored with `cpu_id`; `fallback_buf `only contains 256 bytes.\n\n### PoC\n\nLocal testing with an AddressSanitizer user-space PoC reproduced the same class of size-mismatch over-read as the vulnerable fallback-buffer path. That result is sufficient to ground the advisory in a fresh local reproduction even though the exact end-to-end eBPF path still depends on host BPF capabilities.\n\nTo reproduce the validated behavior locally:\n\n1. create a struct that models `fallback_buf[256]` and `real_size`\n2. populate only the 256-byte fallback buffer\n3. simulate the CPU mismatch path by using the fallback buffer as the source pointer while preserving a much larger `real_size`\n4. perform a read of `real_size` bytes from that 256-byte backing store under ASan\n\nAn equivalent reproducer is:\n\n```c\n// save as /tmp/poc_msgbuf_oob.c\n#include \u003cstdint.h\u003e\n#include \u003cstdio.h\u003e\n#include \u003cstring.h\u003e\n\nstruct msg_buffer {\n  unsigned char fallback_buf[256];\n  uint16_t pos;\n  uint16_t real_size;\n  uint32_t cpu_id;\n};\n\nint main(void) {\n  struct msg_buffer m = {0};\n  unsigned char sink[8192];\n\n  memset(m.fallback_buf, \u0027A\u0027, sizeof(m.fallback_buf));\n  m.real_size = 4096;\n\n  memcpy(sink, m.fallback_buf, m.real_size);\n  printf(\"copied %u bytes from a 256-byte fallback buffer\\n\", m.real_size);\n  return 0;\n}\n```\n\nCompile and run with ASan:\n\n```bash\ncc -fsanitize=address -O1 -g -o /tmp/poc_msgbuf_oob /tmp/poc_msgbuf_oob.c\nASAN_OPTIONS=abort_on_error=1 /tmp/poc_msgbuf_oob\n```\n\nExpected result:\n\n```text\nAddressSanitizer: heap-buffer-overflow or stack-buffer-overflow\n```\n\nThat user-space PoC matches the size-mismatch condition in the vulnerable code path, even though the exact end-to-end eBPF runtime path still requires host BPF attach/load capability.\n\n### Impact\n\nThis is a confidentiality issue in the HTTP tracing path. The vulnerable read occurs in OBI\u0027s local fallback-buffer handling when context propagation is enabled, the `tpinjector` sock_msg path is active, HTTP large-buffer capture is configured with a non-zero size, and a CPU mismatch occurs between producer and consumer contexts. Under those conditions, OBI can over-read from the fallback buffer and export unrelated memory through telemetry.",
  "id": "GHSA-r6c9-g6q5-qrf9",
  "modified": "2026-06-09T10:58:36Z",
  "published": "2026-05-18T20:11:20Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/security/advisories/GHSA-r6c9-g6q5-qrf9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45681"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation/releases/tag/v0.9.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenTelemetry eBPF Instrumentation: CPU-mismatch fallback uses 256-byte buffer with 8KB size"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-45681 (GCVE-0-2026-45681)

FKIE_CVE-2026-45681

GHSA-R6C9-G6Q5-QRF9

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature