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CVE-2026-23111— netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于nft_map_catchall_activate函数中存在反向的生成掩码检查逻辑错误，可能导致事务回滚时元素状态处理不当。

CVSS 7.8 · High EPSS 0.52% · P43

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 24

VendorProduct Version RangeStatus
Linux Linux 25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8< 8c760ba4e36c750379d13569f23f5a6e185333f5 affected
d60be2da67d172aecf866302c91ea11533eca4d9< b9b6573421de51829f7ec1cce76d85f5f6fbbd7f affected
628bd3e49cba1c066228e23d71a852c23e26da73< 42c574c1504aa089a0a142e4c13859327570473d affected
628bd3e49cba1c066228e23d71a852c23e26da73< 1444ff890b4653add12f734ffeffc173d42862dd affected
628bd3e49cba1c066228e23d71a852c23e26da73< 8b68a45f9722f2babe9e7bad00aa74638addf081 affected
628bd3e49cba1c066228e23d71a852c23e26da73< f41c5d151078c5348271ffaf8e7410d96f2d82f8 affected
bc9f791d2593f17e39f87c6e2b3a36549a3705b1 affected
3c7ec098e3b588434a8b07ea9b5b36f04cef1f50 affected
… +16 more rows
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I. Basic Information for CVE-2026-23111

Vulnerability Information
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Vulnerability Title
netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于nft_map_catchall_activate函数中存在反向的生成掩码检查逻辑错误，可能导致事务回滚时元素状态处理不当。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8 ~ 8c760ba4e36c750379d13569f23f5a6e185333f5 -
Linux Linux 6.4 -

II. Public POCs for CVE-2026-23111

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III. Intelligence Information for CVE-2026-23111

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IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-23111

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