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

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{
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        "metrics": [
          {
            "other": {
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                "id": "CVE-2026-45681",
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}

FKIE_CVE-2026-45681

Vulnerability from fkie_nvd - Published: 2026-06-02 16:16 - Updated: 2026-06-03 16:52

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

{
  "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."
    }
  ],
  "id": "CVE-2026-45681",
  "lastModified": "2026-06-03T16:52:16.750",
  "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"
      }
    ]
  },
  "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: 2026-05-18 20:11

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": null,
    "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": "2026-05-18T20:11:20Z",
  "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": "PACKAGE",
      "url": "https://github.com/open-telemetry/opentelemetry-ebpf-instrumentation"
    }
  ],
  "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.

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