CVE-2026-23111

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-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 Software

VendorProductVersion RangeStatus
LinuxLinux25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8 < 8c760ba4e36c750379d13569f23f5a6e185333f5affected
LinuxLinuxd60be2da67d172aecf866302c91ea11533eca4d9 < b9b6573421de51829f7ec1cce76d85f5f6fbbd7faffected
LinuxLinux628bd3e49cba1c066228e23d71a852c23e26da73 < 42c574c1504aa089a0a142e4c13859327570473daffected
LinuxLinux628bd3e49cba1c066228e23d71a852c23e26da73 < 1444ff890b4653add12f734ffeffc173d42862ddaffected
LinuxLinux628bd3e49cba1c066228e23d71a852c23e26da73 < 8b68a45f9722f2babe9e7bad00aa74638addf081affected
LinuxLinux628bd3e49cba1c066228e23d71a852c23e26da73 < f41c5d151078c5348271ffaf8e7410d96f2d82f8affected
LinuxLinuxbc9f791d2593f17e39f87c6e2b3a36549a3705b1affected
LinuxLinux3c7ec098e3b588434a8b07ea9b5b36f04cef1f50affected
LinuxLinuxa136b7942ad2a50de708f76ea299ccb45ac7a7f9affected
LinuxLinuxdc7cdf8cbcbf8b13de1df93f356ec04cdeef5c41affected
LinuxLinux5.15.121 < 5.15.200affected
LinuxLinux6.1.36 < 6.1.163affected
LinuxLinux4.19.316 < 4.20affected
LinuxLinux5.4.262 < 5.5affected
LinuxLinux5.10.188 < 5.11affected
LinuxLinux6.3.10 < 6.4affected
LinuxLinux6.4affected
LinuxLinux0 < 6.4unaffected
LinuxLinux5.15.200 <= 5.15.*unaffected
LinuxLinux6.1.163 <= 6.1.*unaffected
LinuxLinux6.6.124 <= 6.6.*unaffected
LinuxLinux6.12.70 <= 6.12.*unaffected
LinuxLinux6.18.10 <= 6.18.*unaffected
LinuxLinux6.19 <= *unaffected

Weaknesses

ADP Enrichment

Additional References

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

Additional References

kernel: Kernel: Privilege escalation or denial of service in nf_tables via inverted element activity check

Additional References

References