{"cve":"CVE-2026-23111","nvd":{"published":"2026-02-13T14:16:10.283","modified":"2026-10-15T02:18:42.620","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()\n\nnft_map_catchall_activate() has an inverted element activity check\ncompared to its non-catchall counterpart nft_mapelem_activate() and\ncompared to what is logically required.\n\nnft_map_catchall_activate() is called from the abort path to re-activate\ncatchall map elements that were deactivated during a failed transaction.\nIt should skip elements that are already active (they don't need\nre-activation) and process elements that are inactive (they need to be\nrestored). Instead, the current code does the opposite: it skips inactive\nelements and processes active ones.\n\nCompare the non-catchall activate callback, which is correct:\n\n  nft_mapelem_activate():\n    if (nft_set_elem_active(ext, iter->genmask))\n        return 0;   /* skip active, process inactive */\n\nWith the buggy catchall version:\n\n  nft_map_catchall_activate():\n    if (!nft_set_elem_active(ext, genmask))\n        continue;   /* skip inactive, process active */\n\nThe consequence is that when a DELSET operation is aborted,\nnft_setelem_data_activate() is never called for the catchall element.\nFor NFT_GOTO verdict elements, this means nft_data_hold() is never\ncalled to restore the chain->use reference count. Each abort cycle\npermanently decrements chain->use. Once chain->use reaches zero,\nDELCHAIN succeeds and frees the chain while catchall verdict elements\nstill reference it, resulting in a use-after-free.\n\nThis is exploitable for local privilege escalation from an unprivileged\nuser via user namespaces + nftables on distributions that enable\nCONFIG_USER_NS and CONFIG_NF_TABLES.\n\nFix by removing the negation so the check matches nft_mapelem_activate():\nskip active elements, process inactive ones.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416","CWE-672"],"references":["https://git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd","https://git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d","https://git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081","https://git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5","https://git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:23:35.260773158+00:00"},"epss":{"cve":"CVE-2026-23111","score":0.00519,"percentile":0.43849,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}