CVE-2026-23111: Linux kernel · netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 6.8.0-1051.54~22.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 43% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1051.54~22.04.1, 6.8.0-1052.58~22.04.1, 6.8.0-1058.65~22.04.1 +41
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 13 Feb 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
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-8148-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8149-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8152-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-8149-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8162-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?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.
Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate() nft_map_catchall_activate() has an inverted element activity check compared to its non-catchall counterpart nft_mapelem_activate() and compared to what is logically required. nft_map_catchall_activate() is called from the abort path to re-activate catchall map elements that were deactivated during a failed transaction. It should skip elements that are already active (they don't need re-activation) and process elements that are inactive (they need to be restored). Instead, the current code does the opposite: it skips inactive elements and processes active ones. Compare the non-catchall activate callback, which is correct: nft_mapelem_activate(): if (nft_set_elem_active(ext, iter->genmask)) return 0; /* skip active, process inactive */ With the buggy catchall version: nft_map_catchall_activate(): if (!nft_set_elem_active(ext, genmask)) continue; /* skip inactive, process active */ The consequence is that when a DELSET operation is aborted, nft_setelem_data_activate() is never called for the catchall element. For NFT_GOTO verdict elements, this means nft_data_hold() is never called to restore the chain->use reference count. Each abort cycle permanently decrements chain->use. Once chain->use reaches zero, DELCHAIN succeeds and frees the chain while catchall verdict elements still reference it, resulting in a use-after-free. This is exploitable for local privilege escalation from an unprivileged user via user namespaces + nftables on distributions that enable CONFIG_USER_NS and CONFIG_NF_TABLES. Fix by removing the negation so the check matches nft_mapelem_activate(): skip active elements, process inactive ones.
Reports on CVE-2026-23111
References
- ubuntu.com/security/CVE-2026-23111 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23111 (opens in a new tab)
- git.kernel.org/linus/f41c5d151078c5348271ffaf8e7410d96f2d82f8 (opens in a new tab)
- git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd (opens in a new tab)
- git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d (opens in a new tab)
- git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081 (opens in a new tab)
- git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5 (opens in a new tab)
- git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f (opens in a new tab)
- git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8149-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8152-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-8149-2 (opens in a new tab)