Vulnerability Database

374,567

Total vulnerabilities in the database

CVE-2026-23111 — linux / linux_kernel

Use After Free

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.

  • Published: Feb 13, 2026
  • Updated: Mar 19, 2026
  • CVE: CVE-2026-23111
  • Severity: High
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: High
  • Score: 7.8
  • AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Software From Fixed in
linux / linux_kernel 4.19.316 4.20
linux / linux_kernel 5.4.262 5.5
linux / linux_kernel 5.10.188 5.11
linux / linux_kernel 5.15.121 5.15.200
linux / linux_kernel 6.1.36 6.1.163
linux / linux_kernel 6.3.10 6.4
linux / linux_kernel 6.4.1 6.6.124
linux / linux_kernel 6.7 6.12.70
linux / linux_kernel 6.13 6.18.10
linux / linux_kernel 6.4 6.4.x
linux / linux_kernel 6.19-rc1 6.19-rc1.x
linux / linux_kernel 6.19-rc2 6.19-rc2.x
linux / linux_kernel 6.19-rc3 6.19-rc3.x
linux / linux_kernel 6.19-rc4 6.19-rc4.x
linux / linux_kernel 6.19-rc5 6.19-rc5.x
linux / linux_kernel 6.19-rc6 6.19-rc6.x
linux / linux_kernel 6.19-rc7 6.19-rc7.x
linux / linux_kernel 6.19-rc8 6.19-rc8.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

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Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

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