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.
References
Configurations
Configuration 1 (hide)
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History
No history.
Information
Published : 2026-02-13 14:16
Updated : 2026-03-18 13:43
NVD link : CVE-2026-23111
Mitre link : CVE-2026-23111
CVE.ORG link : CVE-2026-23111
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free