HIGH · CVSS 3.1 7.8Public PoCEPSS 0.52% (p43)Threat level 43

CVE-2026-23111: CVE-2026-23111: In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables:…

linux · linux kernel · NVD published 2026-02-13 · posted 2026-06-09 · last modified 2026-10-15

What it 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.

Weakness	CWE-416 CWE-672
CVSS vector	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (source: [email protected])
ATT&CK tactics	Execution → Privilege Escalation

Exploitation evidence

First exploit evidence seen: 2026-06-09 (earliest date across the sources below).

Exploited in the wild

No source on this site lists in-the-wild exploitation yet (CISA KEV, VulnCheck KEV).

Public exploit code

GitHub proof-of-concept repositories

10 public repositories from 10 accounts, first seen 2026-06-09. Most starred: Knz-source/CVE-2026-23111-POC-noddlenpottato (10 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: nomi-sec/PoC-in-GitHub.

How to fix it

Fixed versions

linux linux kernel: upgrade to 4.20 or later (affected from 4.19.316)
linux linux kernel: upgrade to 5.5 or later (affected from 5.4.262)
linux linux kernel: upgrade to 5.11 or later (affected from 5.10.188)
linux linux kernel: upgrade to 5.15.200 or later (affected from 5.15.121)
linux linux kernel: upgrade to 6.1.163 or later (affected from 6.1.36)
linux linux kernel: upgrade to 6.4 or later (affected from 6.3.10)
linux linux kernel: upgrade to 6.6.124 or later (affected from 6.4.1)
linux linux kernel: upgrade to 6.12.70 or later (affected from 6.7)
linux linux kernel: upgrade to 6.18.10 or later (affected from 6.13)

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

MITRE ATT&CK mitigations for this chain

M1050 Exploit Protection (for T1203, T1068) : Security applications that look for behavior used during exploitation such as Windows Defender Exploit Guard (WDEG) and the Enhanced Mitigation Experience Toolkit (EMET) can be used to mitigate some exploitation behavior. Control flow integrity checking is another way to potentially identify and stop a software exploi
M1051 Update Software (for T1203, T1068) : Perform regular software updates to mitigate exploitation risk. Keeping software up-to-date with the latest security patches helps prevent adversaries from exploiting known vulnerabilities in client software, reducing the risk of successful attacks.
M1048 Application Isolation and Sandboxing (for T1203, T1068) : Browser sandboxes can be used to mitigate some of the impact of exploitation, but sandbox escapes may still exist. Other types of virtualization and application microsegmentation may also mitigate the impact of client-side exploitation. Risks of additional exploits and weaknesses in those systems may still exist.
M1019 Threat Intelligence Program (for T1068) : Develop a robust cyber threat intelligence capability to determine what types and levels of threat may use software exploits and 0-days against a particular organization.
M1038 Execution Prevention (for T1068) : Consider blocking the execution of known vulnerable drivers that adversaries may exploit to execute code in kernel mode. Validate driver block rules in audit mode to ensure stability prior to production deployment.

Detection Generic guidance

Execution: Watch for the service process spawning shells or script interpreters (cmd.exe, powershell, sh, bash, python) via EDR process-tree rules.
Privilege Escalation: Alert on processes gaining SYSTEM/root unexpectedly, and on exploitation crashes of privileged services.

Response checklist Generic guidance

Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.