CVE-2026-64089: Linux kernel · batman-adv: tt: fix negative last_changeset_len
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · patch available : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 45% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 20 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
AI-suggested
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.
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.
References
- nvd.nist.gov/vuln/detail/CVE-2026-64089 (opens in a new tab)
- git.kernel.org/stable/c/179eb62506a02d00370bd6478898cb632e10986c (opens in a new tab)
- git.kernel.org/stable/c/22d59c72f4a47ffec121d0610f70d0d70c3c11c8 (opens in a new tab)
- git.kernel.org/stable/c/55dc41fe8821e9a849e147255ad572bc933a9d15 (opens in a new tab)
- git.kernel.org/stable/c/6314089acf0ddf64376fdc0b1420695504c73f52 (opens in a new tab)
- git.kernel.org/stable/c/c424e8519ac78eac5d9f4eecf06208a0d619ec14 (opens in a new tab)
- git.kernel.org/stable/c/d29abf70c665730e249d2ec8e1402095ae26bcee (opens in a new tab)
- git.kernel.org/stable/c/eb235472b52ef36981c5aad330485eaf2382c53b (opens in a new tab)
- git.kernel.org/stable/c/fc92cdfcb295cefa4344d71a527d61b638b7bfc4 (opens in a new tab)
- ubuntu.com/security/CVE-2026-64089 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-64089 (opens in a new tab)
- git.kernel.org/linus/fc92cdfcb295cefa4344d71a527d61b638b7bfc4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8593-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8603-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8610-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8618-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8620-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8620-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8620-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8620-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8663-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8664-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8668-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)