UnratedFix available

UBUNTU-CVE-2026-63387

Type: advisorySource: OSV1 source record

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.

Announced 20 Aug 2026Source revision 1

Original source ↗

UBUNTU-CVE-2026-63387

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:UBUNTU-CVE-2026-63387

libevent

Source reference: /affected/0/package/name

Affected versions: 2.0.21-stable-1
Source reference: /affected/0/versions
2.0.21-stable-1ubuntu1
Source reference: /affected/0/versions
2.0.21-stable-1ubuntu1.14.04.1
Source reference: /affected/0/versions
2.0.21-stable-1ubuntu1.14.04.2
Source reference: /affected/0/versions
2.0.21-stable-1ubuntu1.14.04.2+esm1
Source reference: /affected/0/versions
2.0.21-stable-1ubuntu1.14.04.2+esm2
Source reference: /affected/0/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

libevent

Source reference: /affected/1/package/name

Affected versions: 2.0.21-stable-2
Source reference: /affected/1/versions
2.0.21-stable-2ubuntu0.16.04.1
Source reference: /affected/1/versions
2.0.21-stable-2ubuntu0.16.04.1+esm1
Source reference: /affected/1/versions
2.0.21-stable-2ubuntu0.16.04.1+esm2
Source reference: /affected/1/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

libevent

Source reference: /affected/2/package/name

Affected versions: 2.1.8-stable-4
Source reference: /affected/2/versions
2.1.8-stable-4build1
Source reference: /affected/2/versions
2.1.8-stable-4ubuntu0.1~esm1
Source reference: /affected/2/versions
2.1.8-stable-4ubuntu0.1~esm2
Source reference: /affected/2/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

libevent

Source reference: /affected/3/package/name

Affected versions: 2.1.8-stable-4build1
Source reference: /affected/3/versions
2.1.11-stable-1~exp0
Source reference: /affected/3/versions
2.1.11-stable-1
Source reference: /affected/3/versions
2.1.11-stable-1ubuntu0.1~esm1
Source reference: /affected/3/versions
2.1.11-stable-1ubuntu0.1~esm2
Source reference: /affected/3/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

libevent

Source reference: /affected/4/package/name

Affected versions: 2.1.12-stable-1
Source reference: /affected/4/versions
2.1.12-stable-1build1
Source reference: /affected/4/versions
2.1.12-stable-1build2
Source reference: /affected/4/versions
2.1.12-stable-1build3
Source reference: /affected/4/versions
2.1.12-stable-1ubuntu0.1
Source reference: /affected/4/versions
2.1.12-stable-1ubuntu0.2
Source reference: /affected/4/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

libevent

Source reference: /affected/5/package/name

Affected versions: 2.1.12-stable-9
Source reference: /affected/5/versions
2.1.12-stable-9ubuntu2
Source reference: /affected/5/versions
2.1.12-stable-9ubuntu2.1
Source reference: /affected/5/versions
2.1.12-stable-9ubuntu2.2
Source reference: /affected/5/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

libevent

Source reference: /affected/6/package/name

Affected versions: 2.1.12-stable-10build1
Source reference: /affected/6/versions
2.1.12-stable-10build2
Source reference: /affected/6/versions
2.1.12-stable-10ubuntu0.1
Source reference: /affected/6/versions
Fixed versions: 2.1.12-stable-10ubuntu0.2
Source reference: /affected/6/ranges
Prerequisites: Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

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      "purl": "pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra-legacy%2Ftrusty",
      "ecosystem": "Ubuntu:Pro:14.04:LTS"
    },
    "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",
      "2.0.21-stable-1ubuntu1.14.04.2+esm1",
      "2.0.21-stable-1ubuntu1.14.04.2+esm2"
    ],
    "database_specific": {
      "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"
    },
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    },
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        },
        {
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        },
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        },
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          "binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
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  },
  {
    "ranges": [
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          {
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          }
        ]
      }
    ],
    "package": {
      "name": "libevent",
      "purl": "pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra%2Fbionic",
      "ecosystem": "Ubuntu:Pro:18.04:LTS"
    },
    "versions": [
      "2.1.8-stable-4",
      "2.1.8-stable-4build1",
      "2.1.8-stable-4ubuntu0.1~esm1",
      "2.1.8-stable-4ubuntu0.1~esm2"
    ],
    "database_specific": {
      "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"
    },
    "ecosystem_specific": {
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          "binary_name": "libevent-2.1-6",
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        },
        {
          "binary_name": "libevent-core-2.1-6",
          "binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-extra-2.1-6",
          "binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-openssl-2.1-6",
          "binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-pthreads-2.1-6",
          "binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
        }
      ]
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
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      "purl": "pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra%2Ffocal",
      "ecosystem": "Ubuntu:Pro:20.04:LTS"
    },
    "versions": [
      "2.1.8-stable-4build1",
      "2.1.11-stable-1~exp0",
      "2.1.11-stable-1",
      "2.1.11-stable-1ubuntu0.1~esm1",
      "2.1.11-stable-1ubuntu0.1~esm2"
    ],
    "database_specific": {
      "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"
    },
    "ecosystem_specific": {
      "binaries": [
        {
          "binary_name": "libevent-2.1-7",
          "binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-core-2.1-7",
          "binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-extra-2.1-7",
          "binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-openssl-2.1-7",
          "binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
        },
        {
          "binary_name": "libevent-pthreads-2.1-7",
          "binary_version": "2.1.11-stable-1ubuntu0.1~esm2"
        }
      ]
    }
  },
  {
    "ranges": [
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        "events": [
          {
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          }
        ]
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    ],
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      "name": "libevent",
      "purl": "pkg:deb/ubuntu/libevent?arch=source&distro=jammy",
      "ecosystem": "Ubuntu:22.04:LTS"
    },
    "versions": [
      "2.1.12-stable-1",
      "2.1.12-stable-1build1",
      "2.1.12-stable-1build2",
      "2.1.12-stable-1build3",
      "2.1.12-stable-1ubuntu0.1",
      "2.1.12-stable-1ubuntu0.2"
    ],
    "database_specific": {
      "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"
    },
    "ecosystem_specific": {
      "binaries": [
        {
          "binary_name": "libevent-2.1-7",
          "binary_version": "2.1.12-stable-1ubuntu0.2"
        },
        {
          "binary_name": "libevent-core-2.1-7",
          "binary_version": "2.1.12-stable-1ubuntu0.2"
        },
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          "binary_name": "libevent-extra-2.1-7",
          "binary_version": "2.1.12-stable-1ubuntu0.2"
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          "binary_version": "2.1.12-stable-1ubuntu0.2"
        },
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      "2.1.12-stable-9ubuntu2.2"
    ],
    "database_specific": {
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    },
    "ecosystem_specific": {
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        {
          "binary_name": "libevent-2.1-7t64",
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        },
        {
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        },
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        },
        {
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        },
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        }
      ]
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          }
        ]
      }
    ],
    "package": {
      "name": "libevent",
      "purl": "pkg:deb/ubuntu/libevent?arch=source&distro=resolute",
      "ecosystem": "Ubuntu:26.04:LTS"
    },
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      "2.1.12-stable-10build2",
      "2.1.12-stable-10ubuntu0.1"
    ],
    "database_specific": {
      "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"
    },
    "ecosystem_specific": {
      "binaries": [
        {
          "binary_name": "libevent-2.1-7t64",
          "binary_version": "2.1.12-stable-10ubuntu0.2"
        },
        {
          "binary_name": "libevent-core-2.1-7t64",
          "binary_version": "2.1.12-stable-10ubuntu0.2"
        },
        {
          "binary_name": "libevent-extra-2.1-7t64",
          "binary_version": "2.1.12-stable-10ubuntu0.2"
        },
        {
          "binary_name": "libevent-openssl-2.1-7t64",
          "binary_version": "2.1.12-stable-10ubuntu0.2"
        },
        {
          "binary_name": "libevent-pthreads-2.1-7t64",
          "binary_version": "2.1.12-stable-10ubuntu0.2"
        }
      ],
      "availability": "No subscription required"
    }
  }
]

Publisher severity

No explicit severity was provided.

Event: #33248 · Revision 1
Added to Heist Feed: Sun, 25 Oct 2026 09:03:00 GMT
Publisher date: Thu, 20 Aug 2026 18:16:00 GMT

Read the original announcement