Linux Kernel up to 6.18.9 nf_tables nft_map_catchall_activate reference count

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Summaryinfo

A vulnerability has been found in Linux Kernel up to 5.15.199/6.1.162/6.6.123/6.12.69/6.18.9 and classified as critical. The affected element is the function nft_map_catchall_activate of the component nf_tables. This manipulation causes reference count. This vulnerability is handled as CVE-2026-23111. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 5.15.199/6.1.162/6.6.123/6.12.69/6.18.9 and classified as critical. Affected by this vulnerability is the function nft_map_catchall_activate of the component nf_tables. The manipulation with an unknown input leads to a reference count vulnerability. The CWE definition for the vulnerability is CWE-911. The product uses a reference count to manage a resource, but it does not update or incorrectly updates the reference count. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-23111 since 01/13/2026. The exploitation appears to be easy. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 299034 (Linux Distros Unpatched Vulnerability : CVE-2026-23111), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.200, 6.1.163, 6.6.124, 6.12.70 or 6.18.10 eliminates this vulnerability. Applying the patch 8c760ba4e36c750379d13569f23f5a6e185333f5/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f/42c574c1504aa089a0a142e4c13859327570473d/1444ff890b4653add12f734ffeffc173d42862dd/8b68a45f9722f2babe9e7bad00aa74638addf081/f41c5d151078c5348271ffaf8e7410d96f2d82f8 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (299034) and CERT Bund (WID-SEC-2026-0421). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Google Cloud Platform
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel
  • IBM QRadar SIEM

Productinfo

Type

Vendor

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Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.1
VulDB Meta Temp Score: 7.0

VulDB Base Score: 5.7
VulDB Temp Score: 5.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔒

CNA Base Score: 7.8
CNA Vector (Linux): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Reference count
CWE: CWE-911 / CWE-664
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 299034
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-23111

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.15.200/6.1.163/6.6.124/6.12.70/6.18.10
Patch: 8c760ba4e36c750379d13569f23f5a6e185333f5/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f/42c574c1504aa089a0a142e4c13859327570473d/1444ff890b4653add12f734ffeffc173d42862dd/8b68a45f9722f2babe9e7bad00aa74638addf081/f41c5d151078c5348271ffaf8e7410d96f2d82f8

Timelineinfo

01/13/2026 CVE reserved
02/13/2026 +31 days Advisory disclosed
02/13/2026 +0 days VulDB entry created
06/02/2026 +109 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-23111 (🔒)
GCVE (CVE): GCVE-0-2026-23111
GCVE (VulDB): GCVE-100-345901
CERT Bund: WID-SEC-2026-0421 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 02/13/2026 15:08
Updated: 06/02/2026 19:21
Changes: 02/13/2026 15:08 (59), 02/14/2026 04:39 (2), 03/19/2026 00:58 (12), 05/06/2026 06:38 (7), 06/02/2026 19:21 (11)
Complete: 🔍
Cache ID: 216::103

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