Libevent: Prior to 2.1.13 and 2.2.2-a ...) (CVE-2026-63383)
Description
CVE-2026-63383 is a vulnerability in the libevent library where malformed tagged RPC data is incorrectly handled. This flaw can lead to an out-of-bounds read, potentially causing a denial of service. The issue affects multiple Ubuntu LTS releases including 14.04 through 26.04. Official patches are available for all affected versions, and Ubuntu Pro provides extended support for older releases. The vulnerability is rated medium severity based on its impact and attack vector.
CVSS v4.0
Affected software
pkg:deb/ubuntu/libevent?arch=source&distro=trustypkg:deb/ubuntu/libevent?arch=source&distro=xenialpkg:deb/ubuntu/libevent?arch=source&distro=bionicpkg:deb/ubuntu/libevent?arch=source&distro=focalpkg:deb/ubuntu/libevent?arch=source&distro=jammypkg:deb/ubuntu/libevent?arch=source&distro=noblepkg:deb/ubuntu/libevent?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Libevent versions prior to 2.1.13 and 2.2.2-a contain a vulnerability (CVE-2026-63383) where malformed tagged RPC data is improperly processed, leading to an out-of-bounds read condition. This can cause a denial of service in affected systems. The issue was discovered by Qiu Sihao and affects Ubuntu 14.04 LTS through 26.04 LTS. The vendor advisory from Ubuntu confirms patches are available across all supported LTS versions, with fixes delivered via standard system updates or Ubuntu Pro for legacy releases.
Potential Impact
An attacker can exploit this vulnerability by sending malformed tagged RPC data to trigger an out-of-bounds read, resulting in denial of service. There is no indication of privilege escalation or code execution from this specific flaw. The impact is limited to service disruption on affected Ubuntu systems running vulnerable libevent versions.
Mitigation Recommendations
The vulnerability is addressed by official patches available from Ubuntu for all affected LTS releases. Users should update libevent packages to the fixed versions provided in the Ubuntu security notices. For older releases, Ubuntu Pro with Legacy Support add-on offers fixes. Standard system updates will apply necessary patches, so applying these updates promptly mitigates the risk.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-63383
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:14.04:LTS","Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.04:LTS"]
- Cvss Version
- 4.0
Threat ID: 6a8c4c54acd9273b499be7d5
Added to database: 08/24/2026, 13:51:16 UTC
Last enriched: 09/10/2026, 21:33:22 UTC
Last updated: 10/08/2026, 18:48:47 UTC
Views: 49
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