Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-23111 is a high-severity Use After Free (CWE-416) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 39th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and IA-5 (Authenticator Management) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-23111 is a use-after-free vulnerability (CWE-416) in the Linux kernel's netfilter nf_tables subsystem, stemming from an inverted genmask check in the nft_map_catchall_activate() function. This function, called during abort paths of failed transactions, incorrectly skips inactive catchall map elements and processes active ones, unlike the correct nft_mapelem_activate() counterpart. As a result, catchall elements are not properly reactivated, preventing nft_setelem_data_activate() from being called. For NFT_GOTO verdict elements, this fails to restore the chain->use reference count via nft_data_hold(), leading to permanent decrements until chain->use reaches zero, allowing DELCHAIN to free the chain while elements still reference it.
A local unprivileged attacker can exploit this vulnerability on distributions enabling CONFIG_USER_NS and CONFIG_NF_TABLES by triggering repeated abort cycles during DELSET operations via nftables in a user namespace. This culminates in a use-after-free of the chain structure, enabling local privilege escalation. The vulnerability has a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
Kernel stable patches address the issue by removing the negation in nft_map_catchall_activate()'s activity check, aligning it with nft_mapelem_activate() to skip active elements and process inactive ones for proper restoration. Fixes are available in commits such as 1444ff890b4653add12f734ffeffc173d42862dd, 42c574c1504aa089a0a142e4c13859327570473d, 8b68a45f9722f2babe9e7bad00aa74638addf081, 8c760ba4e36c750379d13569f23f5a6e185333f5, and b9b6573421de51829f7ec1cce76d85f5f6fbbd7f on git.kernel.org/stable.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-6170
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 4 hardening rules · 3 OS baselines
V1.4.3
Mitigating Controls (NIST 800-53 r5) AI
Access enforcement applies current authorizations to every request, directly blocking operations once a resource has been revoked or released.
Authenticator management mandates revocation and replacement procedures that render expired credentials unusable.
Developer testing and evaluation can discover use-after-free bugs through dynamic analysis or fuzzing.
Account lifecycle management includes explicit revocation and disabling steps that stop subsequent operations on released accounts or identifiers.
Identifier management requires deallocation and reuse controls that prevent continued use of released identifiers.
Engineering principles can require memory-safe constructs or languages that structurally avoid introducing use-after-free.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Enforcing managed authorizations and revocations directly prevents post-release operations on credentials or entitlements.
Secure SDLC practices directly incorporate memory-safety tooling and reviews that prevent most use-after-free defects.
Vulnerability identification processes can discover use-after-free issues via scanning or analysis but do not prevent their introduction.
Routine patching removes known use-after-free instances after they have been introduced in released software.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect use-after-free bugs before release.
Enforces timely deletion of resources so they cannot be used after release.
Secure SDLC mandates memory-safety practices that reduce use-after-free defects.
Application security requirements can specify memory-management rules that mitigate use-after-free.
Secure architecture principles include memory-safety design choices that limit use-after-free exposure.
Secure coding standards directly prescribe avoidance of use-after-free patterns.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248592 OL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 8 (1 rule)
- V-230279 RHEL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 9 (1 rule)
- V-257794 RHEL 9 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416