CVE-2026-63387
Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response
02 Description
Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response
03 Exploitation and scoring
- Exploitation
- Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
- SSVC decision
- ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
- AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
- Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
- EPSS probability
- 0.41% probability of exploitation activity in the next 30 days.
- EPSS percentile
- Equal to or higher than the score of 35.5% of scored records. A rank, not a probability.
- NVD base score
- 7.0 (CVSS v3.x), scored by the NVD independently of the CNA.
- NVD CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
- NVD analysis status
- Awaiting Analysis. NVD last modified this record on 2026-10-26.
- Red Hat severity
- Important. Red Hat's rating for its own products, not a CVSS rating.
Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.
04 Metadata
- Published
- 2026-08-20 17:53Z2 MO AGO
- Last updated
- 2026-08-25 15:12Z2 MO AGO
- Reserved
- 2026-07-16
- Assigning CNA
- GitHub_M
- Record state
- PUBLISHED
- Severity
- High (CVSS 7.0)
- CNA CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
- Weaknesses
- Data version
- 5.2
- Document digest
- 079bdbd3a988e73b3f79e8782edf04709760ba2806610a7c4efdd9160f7ece3e
05 Affected products
06 References
07 Fixed in
AlmaLinux 8
- libevent Fixed in 2.1.8-11.el8_10
- libevent-devel Fixed in 2.1.8-11.el8_10
- libevent-doc Fixed in 2.1.8-11.el8_10
Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
AlmaLinux 9
- libevent Fixed in 2.1.13-1.el9_8
- libevent-devel Fixed in 2.1.13-1.el9_8
- libevent-doc Fixed in 2.1.13-1.el9_8
Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
AlmaLinux 10
- libevent Fixed in 2.1.13-1.el10_2
- libevent-devel Fixed in 2.1.13-1.el10_2
- libevent-doc Fixed in 2.1.13-1.el10_2
Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
CloudLinux 8
- libevent Fixed in 2.1.8-11.el8_10
- libevent-devel Fixed in 2.1.8-11.el8_10
- libevent-doc Fixed in 2.1.8-11.el8_10
Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.
Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
CloudLinux 9
- libevent Fixed in 2.1.13-1.el9_8
- libevent-devel Fixed in 2.1.13-1.el9_8
- libevent-doc Fixed in 2.1.13-1.el9_8
Derived from AlmaLinux 9. Partial coverage: only packages taken from AlmaLinux 9 are listed.
Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
CloudLinux 10
- libevent Fixed in 2.1.13-1.el10_2
- libevent-devel Fixed in 2.1.13-1.el10_2
- libevent-doc Fixed in 2.1.13-1.el10_2
Derived from AlmaLinux 10. Partial coverage: only packages taken from AlmaLinux 10 are listed.
Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.
Debian 12
- libevent Fixed in 2.1.12-stable-8+deb12u1
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Debian 13
- libevent Fixed in 2.1.13-stable-1~deb13u1
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Debian 14
- libevent Fixed in 2.1.13-stable-1
Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu 22.04 LTS
- libevent No fix yet
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu 24.04 LTS
- libevent No fix yet
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu 26.04 LTS
- libevent Fixed in 2.1.12-stable-10ubuntu0.2
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu Pro 14.04 LTS
- libevent No fix yet
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu Pro 16.04 LTS
- libevent No fix yet
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu Pro 18.04 LTS
- libevent No fix yet
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
Ubuntu Pro 20.04 LTS
- libevent No fix yet
Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.
A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.