Vulnerability-Lookup

CVE-2026-63387 (GCVE-0-2026-63387)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:53 – Updated: 2026-08-25 15:12

Title

Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response

Summary

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Severity

7 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-25 15:11 UTC

CWE

CWE-121 - Stack-based Buffer Overflow
CWE-193 - Off-by-one Error
CWE-787 - Out-of-bounds Write

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/libevent/libevent/security/adv…	x_refsource_CONFIRM
https://github.com/libevent/libevent/releases/tag…	x_refsource_MISC
https://github.com/libevent/libevent/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
libevent	libevent	Affected: >= 2.2.0-alpha, < 2.2.2-alpha Affected: < 2.1.13	guessed

Show details on NVD website

JSON

To clipboard

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                "id": "CVE-2026-63387",
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FKIE_CVE-2026-63387

Vulnerability from fkie_nvd - Published: 2026-08-20 18:16 - Updated: 2026-08-25 16:17

Severity

7.0 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable
	security-advisories@github.com	https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha
	security-advisories@github.com	https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "libevent",
          "vendor": "libevent",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.2.0-alpha, \u003c 2.2.2-alpha"
            },
            {
              "status": "affected",
              "version": "\u003c 2.1.13"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha."
    }
  ],
  "id": "CVE-2026-63387",
  "lastModified": "2026-08-25T16:17:05.573",
  "metrics": {
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          "attackComplexity": "HIGH",
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          "confidentialityImpact": "LOW",
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MSRC_CVE-2026-63387

Vulnerability from csaf_microsoft - Published: 2026-08-22 01:03 - Updated: 2026-08-25 01:05

Summary

Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response

Notes

Additional Resources: To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

Disclaimer: The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

CVE-2026-63387

7.0 (High)


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

CWE-121 - Stack-based Buffer Overflow

Affected products

Known affected 5 products

Product	Version	Remediation
Unresolved product id: 17084-5	—	None Available
Unresolved product id: 17084-3	—	None Available
Unresolved product id: 17084-2	—	None Available
Unresolved product id: 17084-4	—	None Available
Unresolved product id: 17084-1	—	None Available

References

4 references

URL	Category
https://msrc.microsoft.com/csaf/vex/2026/msrc_cve…	self
https://support.microsoft.com/lifecycle	external
https://www.first.org/cvss	external
https://msrc.microsoft.com/csaf/vex/2026/msrc_cve…	self

JSON

To clipboard

{
  "document": {
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-63387 Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response - VEX",
        "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63387.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response",
    "tracking": {
      "current_release_date": "2026-08-25T01:05:57.000Z",
      "generator": {
        "date": "2026-08-25T07:02:58.235Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-63387",
      "initial_release_date": "2026-08-22T01:03:20.000Z",
      "revision_history": [
        {
          "date": "2026-08-22T01:03:20.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        },
        {
          "date": "2026-08-25T01:05:57.000Z",
          "legacy_version": "2",
          "number": "2",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "2"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version",
                "name": "3.0",
                "product": {
                  "name": "Azure Linux 3.0",
                  "product_id": "17084"
                }
              }
            ],
            "category": "product_name",
            "name": "Azure Linux"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "azl3 fluent-bit 0:3.1.10-6.azl3",
                "product": {
                  "name": "azl3 fluent-bit 0:3.1.10-6.azl3",
                  "product_id": "5"
                }
              }
            ],
            "category": "product_name",
            "name": "fluent-bit"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "azl3 libevent 0:2.1.12-1.azl3",
                "product": {
                  "name": "azl3 libevent 0:2.1.12-1.azl3",
                  "product_id": "3"
                }
              }
            ],
            "category": "product_name",
            "name": "libevent"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "azl3 lldpd 0:1.0.22-1.azl3",
                "product": {
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                  "product_id": "2"
                }
              }
            ],
            "category": "product_name",
            "name": "lldpd"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "azl3 mysql 0:8.0.46-1.azl3",
                "product": {
                  "name": "azl3 mysql 0:8.0.46-1.azl3",
                  "product_id": "4"
                }
              }
            ],
            "category": "product_name",
            "name": "mysql"
          },
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "azl3 ntp 0:4.2.8p17-2.azl3",
                "product": {
                  "name": "azl3 ntp 0:4.2.8p17-2.azl3",
                  "product_id": "1"
                }
              }
            ],
            "category": "product_name",
            "name": "ntp"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "azl3 fluent-bit 0:3.1.10-6.azl3 as a component of Azure Linux 3.0",
          "product_id": "17084-5"
        },
        "product_reference": "5",
        "relates_to_product_reference": "17084"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
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          "product_id": "17084-3"
        },
        "product_reference": "3",
        "relates_to_product_reference": "17084"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
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          "product_id": "17084-2"
        },
        "product_reference": "2",
        "relates_to_product_reference": "17084"
      },
      {
        "category": "default_component_of",
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          "product_id": "17084-1"
        },
        "product_reference": "1",
        "relates_to_product_reference": "17084"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-63387",
      "cwe": {
        "id": "CWE-121",
        "name": "Stack-based Buffer Overflow"
      },
      "notes": [
        {
          "category": "general",
          "text": "GitHub_M",
          "title": "Assigning CNA"
        }
      ],
      "product_status": {
        "known_affected": [
          "17084-5",
          "17084-3",
          "17084-2",
          "17084-4",
          "17084-1"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-63387 Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response - VEX",
          "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63387.json"
        }
      ],
      "remediations": [
        {
          "category": "none_available",
          "date": "2026-08-22T01:03:20.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-5"
          ]
        },
        {
          "category": "none_available",
          "date": "2026-08-22T01:03:20.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-3"
          ]
        },
        {
          "category": "none_available",
          "date": "2026-08-22T01:03:20.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-2"
          ]
        },
        {
          "category": "none_available",
          "date": "2026-08-22T01:03:20.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-4"
          ]
        },
        {
          "category": "none_available",
          "date": "2026-08-22T01:03:20.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-1"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.0,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "temporalScore": 7.0,
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
            "version": "3.1"
          },
          "products": [
            "17084-5",
            "17084-3",
            "17084-2",
            "17084-4",
            "17084-1"
          ]
        }
      ],
      "title": "Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response"
    }
  ]
}

ubuntu-cve-2026-63387

Vulnerability from osv_ubuntu

Published

2026-08-21 00:00

Modified

2026-08-24 07:37

Summary

Details

(Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-a ...)

Severity

7.0 (High)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-63387	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-63387	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2"
          },
          {
            "binary_name": "libevent-core-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2"
          },
          {
            "binary_name": "libevent-extra-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2"
          },
          {
            "binary_name": "libevent-openssl-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2"
          },
          {
            "binary_name": "libevent-pthreads-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:14.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-1ubuntu1.14.04.2?arch=source\u0026distro=trusty"
      },
      "ranges": [
        {
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            {
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            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
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        "2.0.21-stable-1ubuntu1",
        "2.0.21-stable-1ubuntu1.14.04.1",
        "2.0.21-stable-1ubuntu1.14.04.2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.0-5",
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          },
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            "binary_name": "libevent-core-2.0-5",
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          },
          {
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          }
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      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-2ubuntu0.16.04.1?arch=source\u0026distro=xenial"
      },
      "ranges": [
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            }
          ],
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        }
      ],
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        "2.0.21-stable-2ubuntu0.16.04.1"
      ]
    },
    {
      "ecosystem_specific": {
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          },
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          },
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            "binary_name": "libevent-pthreads-2.1-6",
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        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
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        "purl": "pkg:deb/ubuntu/libevent@2.1.8-stable-4build1?arch=source\u0026distro=bionic"
      },
      "ranges": [
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    },
    {
      "ecosystem_specific": {
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      },
      "package": {
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        "name": "libevent",
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      },
      "ranges": [
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      },
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        "name": "libevent",
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      },
      "ranges": [
        {
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            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.12-stable-1",
        "2.1.12-stable-1build1",
        "2.1.12-stable-1build2",
        "2.1.12-stable-1build3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
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          },
          {
            "binary_name": "libevent-core-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2"
          },
          {
            "binary_name": "libevent-extra-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2"
          },
          {
            "binary_name": "libevent-openssl-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-9ubuntu2?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
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            {
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            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.12-stable-9",
        "2.1.12-stable-9ubuntu2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7t64",
            "binary_version": "2.1.12-stable-10build2"
          },
          {
            "binary_name": "libevent-core-2.1-7t64",
            "binary_version": "2.1.12-stable-10build2"
          },
          {
            "binary_name": "libevent-extra-2.1-7t64",
            "binary_version": "2.1.12-stable-10build2"
          },
          {
            "binary_name": "libevent-openssl-2.1-7t64",
            "binary_version": "2.1.12-stable-10build2"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7t64",
            "binary_version": "2.1.12-stable-10build2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-10build2?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
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            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.12-stable-10build1",
        "2.1.12-stable-10build2"
      ]
    }
  ],
  "aliases": [],
  "details": "(Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-a ...)",
  "id": "UBUNTU-CVE-2026-63387",
  "modified": "2026-08-24T07:37:25Z",
  "published": "2026-08-21T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-63387"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63387"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-63387"
  ]
}

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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-63387 (GCVE-0-2026-63387)

FKIE_CVE-2026-63387

MSRC_CVE-2026-63387

ubuntu-cve-2026-63387

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature