USN-8840-1 (UBUNTU-CVE-2026-63387)
Vulnerability from osv_ubuntu – Published: 2026-09-28 20:05 – Updated: 2026-09-28 20:05 – Source website
VLAI
Summary
libevent vulnerabilities
Details
Michał Majchrowicz and Marcin Wyczechowski discovered that libevent incorrectly handled certain DNS responses. A remote attacker could possibly use this issue to cause a denial of service or execute arbitrary code. (CVE-2026-63387)
It was discovered that libevent incorrectly handled certain connections. A local attacker could possibly use this issue to cause a denial of service or execute arbitrary code. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-63388)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"database_specific": {
"cves_map": {
"cves": [],
"ecosystem": "Ubuntu:Pro:14.04:LTS"
}
},
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "libevent-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-core-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-extra-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-openssl-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
},
{
"binary_name": "libevent-pthreads-2.0-5",
"binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-1ubuntu1.14.04.2+esm2?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.0.21-stable-1ubuntu1.14.04.2+esm2"
}
],
"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",
"2.0.21-stable-1ubuntu1.14.04.2+esm1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [],
"ecosystem": "Ubuntu:Pro:16.04:LTS"
}
},
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "libevent-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-core-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-extra-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-openssl-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
},
{
"binary_name": "libevent-pthreads-2.0-5",
"binary_version": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-2ubuntu0.16.04.1+esm2?arch=source\u0026distro=esm-infra-legacy/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.0.21-stable-2ubuntu0.16.04.1+esm2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.0.21-stable-2",
"2.0.21-stable-2ubuntu0.16.04.1",
"2.0.21-stable-2ubuntu0.16.04.1+esm1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2026-63388",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:Pro:18.04:LTS"
}
},
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "libevent-2.1-6",
"binary_version": "2.1.8-stable-4ubuntu0.1~esm2"
},
{
"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"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.8-stable-4ubuntu0.1~esm2?arch=source\u0026distro=esm-infra/bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.8-stable-4ubuntu0.1~esm2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.1.8-stable-4",
"2.1.8-stable-4build1",
"2.1.8-stable-4ubuntu0.1~esm1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2026-63388",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:Pro:20.04:LTS"
}
},
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
"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"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.11-stable-1ubuntu0.1~esm2?arch=source\u0026distro=esm-infra/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.11-stable-1ubuntu0.1~esm2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.1.8-stable-4build1",
"2.1.11-stable-1~exp0",
"2.1.11-stable-1",
"2.1.11-stable-1ubuntu0.1~esm1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2026-63388",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:22.04:LTS"
}
},
"ecosystem_specific": {
"availability": "No subscription required",
"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"
},
{
"binary_name": "libevent-extra-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
},
{
"binary_name": "libevent-openssl-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
},
{
"binary_name": "libevent-pthreads-2.1-7",
"binary_version": "2.1.12-stable-1ubuntu0.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-1ubuntu0.2?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.12-stable-1ubuntu0.2"
}
],
"type": "ECOSYSTEM"
}
],
"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"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2026-63388",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:24.04:LTS"
}
},
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "libevent-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-core-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-extra-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-openssl-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
},
{
"binary_name": "libevent-pthreads-2.1-7t64",
"binary_version": "2.1.12-stable-9ubuntu2.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-9ubuntu2.2?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.12-stable-9ubuntu2.2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.1.12-stable-9",
"2.1.12-stable-9ubuntu2",
"2.1.12-stable-9ubuntu2.1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2026-63387",
"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"
}
]
},
{
"id": "CVE-2026-63388",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:26.04:LTS"
}
},
"ecosystem_specific": {
"availability": "No subscription required",
"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"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "libevent",
"purl": "pkg:deb/ubuntu/libevent@2.1.12-stable-10ubuntu0.2?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.12-stable-10ubuntu0.2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.1.12-stable-10build1",
"2.1.12-stable-10build2",
"2.1.12-stable-10ubuntu0.1"
]
}
],
"aliases": [],
"details": "Micha\u0142 Majchrowicz and Marcin Wyczechowski discovered that libevent\nincorrectly handled certain DNS responses. A remote attacker could possibly\nuse this issue to cause a denial of service or execute arbitrary code.\n(CVE-2026-63387)\n\nIt was discovered that libevent incorrectly handled certain connections. A\nlocal attacker could possibly use this issue to cause a denial of service\nor execute arbitrary code. This issue only affected Ubuntu 18.04 LTS,\nUbuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS.\n(CVE-2026-63388)",
"id": "USN-8840-1",
"modified": "2026-09-28T20:05:19Z",
"published": "2026-09-28T20:05:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://ubuntu.com/security/notices/USN-8840-1"
},
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-63387"
},
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-63388"
}
],
"related": [],
"schema_version": "1.7.0",
"summary": "libevent vulnerabilities",
"upstream": [
"UBUNTU-CVE-2026-63387",
"UBUNTU-CVE-2026-63388"
]
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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- 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.
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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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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