CVE-2026-23111

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.

Gravité et risque d'exploitation

CVE-2026-23111 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.52 %, ce qui la place devant 42.9 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <5.11, <=6.1.*, 6.6.124, <=6.12.*, 6.1.36, 0, 6.12.70, 628bd3e49cba1c066228e23d71a852c23e26da73, dc7cdf8cbcbf8b13de1df93f356ec04cdeef5c41, <b9b6573421de51829f7ec1cce76d85f5f6fbbd7f, 6.18.10, 6.4, <8b68a45f9722f2babe9e7bad00aa74638addf081, 5.15.121, <4.20, 3c7ec098e3b588434a8b07ea9b5b36f04cef1f50, <=6.6.*, 6.3.10, 6.1.163, <8c760ba4e36c750379d13569f23f5a6e185333f5, <1444ff890b4653add12f734ffeffc173d42862dd, <6.4, a136b7942ad2a50de708f76ea299ccb45ac7a7f9, 4.19.316, <5.5, <=6.18.*, bc9f791d2593f17e39f87c6e2b3a36549a3705b1, <5.15.200, <=*, <=5.15.*, <42c574c1504aa089a0a142e4c13859327570473d, 6.19, d60be2da67d172aecf866302c91ea11533eca4d9, <6.1.163, 25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8, 5.4.262, 5.10.188, <f41c5d151078c5348271ffaf8e7410d96f2d82f8, 5.15.200) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5
• https://git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f
• https://git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d
• https://git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd
• https://git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081
• https://git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8