CVE-2026-23111High· 7.8▾ MidnightPoC availableIn 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-…
▾ Midnight zone — Critical, or high with PoC / in-the-wild
impact 42.9 · likelihood 0.1 · exploitation 12
A public proof-of-concept already exists for this vulnerability — see Exploit availability below.
Public exploit / PoC code seen in 1 source. Availability, not in-the-wild use.
Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Jul 3.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.3%
10 GitHub repos
0.3% → 0.5%
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.
linux_kernel >= 4.19.316, < 4.20linux_kernel >= 5.4.262, < 5.5linux_kernel >= 5.10.188, < 5.11linux_kernel >= 5.15.121, < 5.15.200linux_kernel >= 6.1.36, < 6.1.163linux_kernel >= 6.3.10, < 6.4linux_kernel >= 6.4.1, < 6.6.124linux_kernel >= 6.7, < 6.12.70linux_kernel >= 6.13, < 6.18.10linux_kernel = 6.4linux_kernel = 6.19Upgrade past the affected range:
linux_kernel 6.18.10Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
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