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CVE

CVE-2026-23111

Linux · Linux kernel

First Reported
Jun 8, 2026
Latest Reported
Jun 8, 2026
Articles
1
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IOC
0
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CVE Enrichment

CVSS
7.8 HIGH
EPSS
0.52%
EPSS Percentile
44.15%
CISA KEV
Not listed

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.

Technical Details

CVSS Version
3.1
CNA / NVD Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
13-Feb-2026 21:16
Last Modified
15-Oct-2026 09:18
EPSS Date
2026-10-31
CWE
CWE-416, CWE-672

CVSS Vector

CVSS:3.1 AV:L / AC:L / PR:L / UI:N / S:U / C:H / I:H / A:H

Affected Products / Versions

References

Last enrichment sync: 31-Oct-2026 23:07
Sources: NVD · FIRST EPSS · CISA KEV
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Reported Context (1)

People (1)

Oliver Sieber1 related article

MITRE ATT&CK (2)

T10681 related articleT16111 related article

Products (4)

Debian Linux1 related articleLinux kernel1 related articleRHEL1 related articleUbuntu1 related article

Note: Related entities, including threat actors, malware, CVEs, MITRE ATT&CK techniques, vendors, products, tools, countries, and industries, are shown when they appear in the same reporting. Their presence does not necessarily mean they were targeted, compromised, vulnerable, responsible for the activity, or directly involved in the incident.