--- id: CVE-2026-23111 title: >- 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-… summary: >- 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-… severity: high cvss: 7.8 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-416 - CWE-672 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 4.19.316, < 4.20' - 'linux_kernel >= 5.4.262, < 5.5' - 'linux_kernel >= 5.10.188, < 5.11' - 'linux_kernel >= 5.15.121, < 5.15.200' - 'linux_kernel >= 6.1.36, < 6.1.163' - 'linux_kernel >= 6.3.10, < 6.4' - 'linux_kernel >= 6.4.1, < 6.6.124' - 'linux_kernel >= 6.7, < 6.12.70' - 'linux_kernel >= 6.13, < 6.18.10' - linux_kernel = 6.4 - linux_kernel = 6.19 patched: - linux_kernel 6.18.10 published: '2026-02-13' updated: '2026-06-30' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-23111' references: - url: 'https://git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://access.redhat.com/errata/RHSA-2026:10108' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:10996' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:18134' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:6570' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:9112' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/security/cve/CVE-2026-23111' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: >- https://blog.exodusintel.com/2026/06/08/off-by-exploiting-a-use-after-free-in-the-linux-kernel/ label: 134c704f-9b21-4f2e-91b3-4a467353bcc0 - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2439687' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://cert-portal.siemens.com/productcert/html/ssa-253495.html' label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23111.json label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c tags: - nvd - cve.org - exploit-available epss: 0.00489 epssPercentile: 0.39409 ingestedAt: '2026-07-03T18:53:52.422Z' ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-06-09T13:07:47.429787Z' exploits: github: 10 githubRepos: - 'https://github.com/HORKimhab/CVE-2026-23111' - 'https://github.com/criann/check-cve-2026-23111' - 'https://github.com/0xBlackash/CVE-2026-23111' checkedAt: '2026-09-25T08:20:53.016Z' exploitAvailable: true --- ## Overview 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. ## Affected - `linux_kernel >= 4.19.316, < 4.20` - `linux_kernel >= 5.4.262, < 5.5` - `linux_kernel >= 5.10.188, < 5.11` - `linux_kernel >= 5.15.121, < 5.15.200` - `linux_kernel >= 6.1.36, < 6.1.163` - `linux_kernel >= 6.3.10, < 6.4` - `linux_kernel >= 6.4.1, < 6.6.124` - `linux_kernel >= 6.7, < 6.12.70` - `linux_kernel >= 6.13, < 6.18.10` - `linux_kernel = 6.4` - `linux_kernel = 6.19` ## Remediation Upgrade past the affected range: - `linux_kernel 6.18.10`