In the Linux kernel, the following vulnerability has been resolved: batman-adv: tt: fix negative last_changeset_len… (CVE-2026-64089)
Description
A vulnerability in the Linux kernel's batman-adv mesh networking subsystem was resolved. The issue involved a signed 16-bit integer field last_changeset_len that could wrap to a negative value when assigned a value greater than 32767, leading to uninitialized memory usage during buffer population. This flaw was fixed by changing the field to an unsigned 16-bit integer to prevent sign extension errors. The vulnerability affects multiple Linux kernel versions prior to specific 5.15.x updates. A high severity CVSS score of 9.8 indicates critical impact potential. Official patches are available and should be applied. No known exploits are reported in the wild.
CVSS v3.1
Score 9.8critical
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel's batman-adv subsystem had a vulnerability (CVE-2026-64089) caused by a signed 16-bit integer field last_changeset_len wrapping to a negative value when assigned values above 32767. This caused improper sign extension when the value was widened to a 32-bit integer, leading to allocation of a full-sized buffer that was only partially populated, leaving uninitialized memory. The fix involved changing last_changeset_len to an unsigned 16-bit integer (u16) to avoid negative sign extension. Affected versions include Linux kernel versions prior to 5.15.0-1112.119~20.04.1 and related 5.15.x versions. The vulnerability has a CVSS 3.1 score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating network exploitable with no privileges or user interaction required, and high confidentiality, integrity, and availability impact. Official patches are available from Ubuntu and other Linux distributions, and users should update to fixed kernel versions. No known active exploitation has been reported.
Potential Impact
If exploited, this vulnerability could allow an attacker to cause the kernel to use uninitialized memory, potentially leading to information disclosure, system instability, or other impacts affecting confidentiality, integrity, and availability. The CVSS score of 9.8 reflects critical impact with network attack vector and no required privileges or user interaction. However, no known exploits are currently reported in the wild.
Mitigation Recommendations
An official fix is available and should be applied by updating the Linux kernel to the patched versions. Ubuntu has released security notices (USN-8575-1 and USN-8576-1) with updated kernel packages addressing this and other vulnerabilities. After applying updates, a system reboot is required. Due to ABI changes, third-party kernel modules may need recompilation and reinstallation. Users should follow vendor instructions for updating and rebuilding kernel modules as necessary.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-7jfx-377j-9v79
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-64089"]
- Cvss Version
- 3.1
Threat ID: 6a5d27a92a4a8d598912b8b9
Added to database: 07/19/2026, 19:38:17 UTC
Last enriched: 09/07/2026, 19:09:30 UTC
Last updated: 10/09/2026, 06:48:18 UTC
Views: 83
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