CVE-2026-31551: Linux kernel · wifi: mac80211: Fix static_branch_dec() underflow for aql_disable.
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · patch available : update Linux kernel when convenient.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 24 Apr 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
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-40.40?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1019.19?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1020.20?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1020.22?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available and should be applied to affected Linux kernel versions. The vendor advisory from Ubuntu confirms that this issue has been fixed. Users should update to a fixed kernel version to remediate the vulnerability.
Description
A vulnerability in the Linux kernel's mac80211 wifi subsystem was fixed to address a static_branch_dec() underflow caused by improper serialization of concurrent writes to debugfs. The issue was reported by syzbot and involves a race condition in aql_enable_write() where the static key state may change between checks and updates, leading to underflow. This flaw could cause a kernel crash (denial of service). The vulnerability affects multiple Linux kernel versions and has been patched.
References
- ubuntu.com/security/CVE-2026-31551 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-31551 (opens in a new tab)
- git.kernel.org/linus/b94ae8e0d5fe1bdbbfdc3854ff6ce98f6876a828 (opens in a new tab)
- git.kernel.org/stable/c/256f7d4c11235d0569f78413c41dc89d2dc1557c (opens in a new tab)
- git.kernel.org/stable/c/29a1a350afcd28a2150bd73b8bd83eac3480f13e (opens in a new tab)
- git.kernel.org/stable/c/5ba05436f15d16ae7ab04b880e8bf8d440be892b (opens in a new tab)
- git.kernel.org/stable/c/787152497ac763deab16f6f4b7ce79aaeb3eb7e8 (opens in a new tab)
- git.kernel.org/stable/c/8bb90ff77326c34e75b573b1febdd9586fec5aba (opens in a new tab)
- git.kernel.org/stable/c/b24763d32d5b4ada766deca4b42d6766272fef0c (opens in a new tab)
- git.kernel.org/stable/c/b94ae8e0d5fe1bdbbfdc3854ff6ce98f6876a828 (opens in a new tab)
- ubuntu.com/security/notices/USN-8567-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-1 (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-8574-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8596-1 (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-8597-1 (opens in a new tab)