Vulnerability-Lookup

CVE-2026-63388 (GCVE-0-2026-63388)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:44 – Updated: 2026-08-21 21:46

Title

Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept

Summary

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address. Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, and the evhttp accept path can pass a 110-byte sockaddr from accept() into the 28-byte field. An unauthenticated local peer able to connect to an AF_UNIX listener can overwrite the adjacent dns_request pointer and heap data, causing memory corruption with confidentiality, integrity, and availability impact. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Severity

8.4 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-21 21:00 UTC

CWE

CWE-617 - Reachable Assertion
CWE-787 - Out-of-bounds Write

Assigner

GitHub_M mitre root

References

5 references

URL	Tags
https://github.com/libevent/libevent/security/adv…	x_refsource_CONFIRM
https://github.com/libevent/libevent/commit/52057…	x_refsource_MISC
https://github.com/libevent/libevent/commit/ef38f…	x_refsource_MISC
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: < 2.1.13 Affected: >= 2.2.0-alpha, < 2.2.2-alpha	guessed

Show details on NVD website

JSON

To clipboard

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              "content": {
                "id": "CVE-2026-63388",
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                "role": "CISA Coordinator",
                "timestamp": "2026-08-21T21:00:24.903079Z",
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            "confidentialityImpact": "HIGH",
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FKIE_CVE-2026-63388

Vulnerability from fkie_nvd - Published: 2026-08-20 18:16 - Updated: 2026-08-21 22:16

Severity

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

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/libevent/libevent/commit/52057cb33d0c20c0a0453fbabe6c0c96854931b9
	security-advisories@github.com	https://github.com/libevent/libevent/commit/ef38f926e9cd1f082416c6fff13587bc1f431d72
	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-cvq5-vrvr-j338

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "libevent",
          "vendor": "libevent",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.1.13"
            },
            {
              "status": "affected",
              "version": "\u003e= 2.2.0-alpha, \u003c 2.2.2-alpha"
            }
          ]
        }
      ],
      "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 a heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address. Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, and the evhttp accept path can pass a 110-byte sockaddr from accept() into the 28-byte field. An unauthenticated local peer able to connect to an AF_UNIX listener can overwrite the adjacent dns_request pointer and heap data, causing memory corruption with confidentiality, integrity, and availability impact. This issue is fixed in versions 2.1.13 and 2.2.2-alpha."
    }
  ],
  "id": "CVE-2026-63388",
  "lastModified": "2026-08-21T22:16:42.567",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 8.4,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
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        "impactScore": 5.9,
        "source": "security-advisories@github.com",
        "type": "Secondary"
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    },
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      "url": "https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha"
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}

MSRC_CVE-2026-63388

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

Summary

Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept

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-2026-63388

8.4 (High)


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

CWE-617 - Reachable Assertion

Affected products

Known affected 1 product

Product	Identifier	Version	Remediation
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-2026-63388 Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept - VEX",
        "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63388.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: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept",
    "tracking": {
      "current_release_date": "2026-08-22T01:03:33.000Z",
      "generator": {
        "date": "2026-08-23T07:01:40.611Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-63388",
      "initial_release_date": "2026-08-22T01:03:33.000Z",
      "revision_history": [
        {
          "date": "2026-08-22T01:03:33.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "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 libevent 0:2.1.12-1.azl3",
                "product": {
                  "name": "azl3 libevent 0:2.1.12-1.azl3",
                  "product_id": "1"
                }
              }
            ],
            "category": "product_name",
            "name": "libevent"
          }
        ],
        "category": "vendor",
        "name": "Microsoft"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "azl3 libevent 0:2.1.12-1.azl3 as a component of Azure Linux 3.0",
          "product_id": "17084-1"
        },
        "product_reference": "1",
        "relates_to_product_reference": "17084"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-63388",
      "cwe": {
        "id": "CWE-617",
        "name": "Reachable Assertion"
      },
      "notes": [
        {
          "category": "general",
          "text": "GitHub_M",
          "title": "Assigning CNA"
        }
      ],
      "product_status": {
        "known_affected": [
          "17084-1"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-63388 Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept - VEX",
          "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63388.json"
        }
      ],
      "remediations": [
        {
          "category": "none_available",
          "date": "2026-08-22T01:03:33.000Z",
          "details": "There is no fix available for this vulnerability as of now",
          "product_ids": [
            "17084-1"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "LOCAL",
            "availabilityImpact": "HIGH",
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "temporalScore": 8.4,
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "products": [
            "17084-1"
          ]
        }
      ],
      "title": "Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept"
    }
  ]
}

ubuntu-cve-2026-63388

Vulnerability from osv_ubuntu

Published

2026-08-21 00:00

Modified

2026-08-21 00:00

Summary

Details

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

Severity

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-63388	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-63388	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": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.0.21-stable-1",
        "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",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1"
          },
          {
            "binary_name": "libevent-core-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1"
          },
          {
            "binary_name": "libevent-extra-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1"
          },
          {
            "binary_name": "libevent-openssl-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1"
          },
          {
            "binary_name": "libevent-pthreads-2.0-5",
            "binary_version": "2.0.21-stable-2ubuntu0.16.04.1"
          }
        ]
      },
      "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": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.0.21-stable-2",
        "2.0.21-stable-2ubuntu0.16.04.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-6",
            "binary_version": "2.1.8-stable-4build1"
          },
          {
            "binary_name": "libevent-core-2.1-6",
            "binary_version": "2.1.8-stable-4build1"
          },
          {
            "binary_name": "libevent-extra-2.1-6",
            "binary_version": "2.1.8-stable-4build1"
          },
          {
            "binary_name": "libevent-openssl-2.1-6",
            "binary_version": "2.1.8-stable-4build1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-6",
            "binary_version": "2.1.8-stable-4build1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.8-stable-4build1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.8-stable-4",
        "2.1.8-stable-4build1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7",
            "binary_version": "2.1.11-stable-1"
          },
          {
            "binary_name": "libevent-core-2.1-7",
            "binary_version": "2.1.11-stable-1"
          },
          {
            "binary_name": "libevent-extra-2.1-7",
            "binary_version": "2.1.11-stable-1"
          },
          {
            "binary_name": "libevent-openssl-2.1-7",
            "binary_version": "2.1.11-stable-1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7",
            "binary_version": "2.1.11-stable-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.11-stable-1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.8-stable-4build1",
        "2.1.11-stable-1~exp0",
        "2.1.11-stable-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libevent-2.1-7",
            "binary_version": "2.1.12-stable-1build3"
          },
          {
            "binary_name": "libevent-core-2.1-7",
            "binary_version": "2.1.12-stable-1build3"
          },
          {
            "binary_name": "libevent-extra-2.1-7",
            "binary_version": "2.1.12-stable-1build3"
          },
          {
            "binary_name": "libevent-openssl-2.1-7",
            "binary_version": "2.1.12-stable-1build3"
          },
          {
            "binary_name": "libevent-pthreads-2.1-7",
            "binary_version": "2.1.12-stable-1build3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-1build3?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "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": [
          {
            "binary_name": "libevent-2.1-7t64",
            "binary_version": "2.1.12-stable-9ubuntu2"
          },
          {
            "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": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "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": [
        {
          "events": [
            {
              "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-2026-63388",
  "modified": "2026-08-21T00:00:00Z",
  "published": "2026-08-21T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-63388"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63388"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-63388"
  ]
}

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-2026-63388 (GCVE-0-2026-63388)

FKIE_CVE-2026-63388

MSRC_CVE-2026-63388

ubuntu-cve-2026-63388

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature