# CVE-2026-23111

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.

- Page: https://www.vulneraibility.com/cve/CVE-2026-23111
- CVSS: 7.8
- Known exploited: not in CISA KEV as of our last sync
- EPSS: 1.13% (percentile 66.9)
- Unvetted proof-of-concept code on GitHub: 10 GitHub proofs of concept (first 2026-06-09)
- CISA SSVC: exploitation none, automatable no, technical impact total (assessed 2026-06-09)
- Weakness: CWE-416, CWE-672
- Published: 2026-02-13

## Affected versions

- Linux: affected >= 25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8 and < 8c760ba4e36c750379d13569f23f5a6e185333f5; >= d60be2da67d172aecf866302c91ea11533eca4d9 and < b9b6573421de51829f7ec1cce76d85f5f6fbbd7f; >= 628bd3e49cba1c066228e23d71a852c23e26da73 and < 42c574c1504aa089a0a142e4c13859327570473d; >= 628bd3e49cba1c066228e23d71a852c23e26da73 and < 1444ff890b4653add12f734ffeffc173d42862dd; >= 628bd3e49cba1c066228e23d71a852c23e26da73 and < 8b68a45f9722f2babe9e7bad00aa74638addf081; >= 628bd3e49cba1c066228e23d71a852c23e26da73 and < f41c5d151078c5348271ffaf8e7410d96f2d82f8; bc9f791d2593f17e39f87c6e2b3a36549a3705b1; 3c7ec098e3b588434a8b07ea9b5b36f04cef1f50; a136b7942ad2a50de708f76ea299ccb45ac7a7f9; dc7cdf8cbcbf8b13de1df93f356ec04cdeef5c41; >= 5.15.121 and < 5.15.200; >= 6.1.36 and < 6.1.163; >= 4.19.316 and < 4.20; >= 5.4.262 and < 5.5; >= 5.10.188 and < 5.11; >= 6.3.10 and < 6.4; 6.4; fixed in < 6.4, >= 5.15.200 and <= 5.15.*, >= 6.1.163 and <= 6.1.*, >= 6.6.124 and <= 6.6.*, >= 6.12.70 and <= 6.12.*, >= 6.18.10 and <= 6.18.*, >= 6.19 and <= *

A version outside these ranges is not a statement that it is unaffected.

## References

- [other] https://git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5
- [other] https://git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f
- [other] https://git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d
- [other] https://git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd
- [other] https://git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081
- [other] https://git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8
- [other] https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- [other] https://cert-portal.siemens.com/productcert/html/ssa-253495.html
- [other] https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- [other] https://cert-portal.siemens.com/productcert/html/ssa-457936.html
- [other] https://blog.exodusintel.com/2026/06/08/off-by-exploiting-a-use-after-free-in-the-linux-kernel/
- [other] https://access.redhat.com/security/cve/CVE-2026-23111
- [other] https://bugzilla.redhat.com/show_bug.cgi?id=2439687
- [other] https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23111.json
- [advisory] https://access.redhat.com/errata/RHSA-2026:10996
- [advisory] https://access.redhat.com/errata/RHSA-2026:18134
- [advisory] https://access.redhat.com/errata/RHSA-2026:10108
- [advisory] https://access.redhat.com/errata/RHSA-2026:9112
- [advisory] https://access.redhat.com/errata/RHSA-2026:6570
- [advisory] https://access.redhat.com/errata/RHSA-2026:62639
- [advisory] https://access.redhat.com/errata/RHSA-2026:62641

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.