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Vulnerability record · CVE-2026-23351 · published 25 March 2026

CVE-2026-23351: Linux kernel use after free vulnerability

Linux · Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_set_pipapo: split gc into unlink and reclaim phase Yiming Qian reports Use-after-free in the pipapo set type: Under a large number of expired elements, commit-time GC can run for a very long time in a non-preemptible context, triggering soft lockup warnings and RCU stall reports (local denial of service). We must split GC in an unlink and a reclaim phase. We cannot queue elements for freeing until pointers have been swapped. Expired elements are still exposed to both the packet path and userspace dumpers via the live copy of the data structure. call_rcu() does not protect us: dump operations or element lookups starting after call_rcu has fired can still observe the free'd element, unless the commit phase has made enough progress to swap the clone and live pointers before any new reader has picked up the old version. This a similar approach as done recently for the rbtree backend in commit 35f83a75529a ("netfilter: nft_set_rbtree: don't gc elements on insert").

7.8 CVSS 3.1 High EPSS 0.13% · top 98.1% CWE-416 · Use after free
7.8CVSS 3.1 base score
0.13%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References
14 Jul 2026Last modified by NVD

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_set_pipapo: split gc into unlink and reclaim phase Yiming Qian reports Use-after-free in the pipapo set type: Under a large number of expired elements, commit-time GC can run for a very long time in a non-preemptible context, triggering soft lockup warnings and RCU stall reports (local denial of service). We must split GC in an unlink and a reclaim phase. We cannot queue elements for freeing until pointers have been swapped. Expired elements are still exposed to both the packet path and userspace dumpers via the live copy of the data structure. call_rcu() does not protect us: dump operations or element lookups starting after call_rcu has fired can still observe the free'd element, unless the commit phase has made enough progress to swap the clone and live pointers before any new reader has picked up the old version. This a similar approach as done recently for the rbtree backend in commit 35f83a75529a ("netfilter: nft_set_rbtree: don't gc elements on insert").

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://git.kernel.org/stable/c/16f3595c0441d87dfa005c47d8f95be213afaa9e Patch
https://git.kernel.org/stable/c/500a50a301ce962b019ab95053ac70264fec2c21 Patch
https://git.kernel.org/stable/c/65ca51b9fb85477ab92a04295aed34b38f7c062e Patch
https://git.kernel.org/stable/c/7864c667aed01a58b87ca518a631322cd0ac34c0 Patch
https://git.kernel.org/stable/c/9df95785d3d8302f7c066050117b04cd3c2048c2 Patch
https://git.kernel.org/stable/c/aff13667708dfa0dce136b8efd81baa9fa6ef261 Patch
https://git.kernel.org/stable/c/c0f1f85097ac2b6e7d750fe4d05807985cd3fd3a Patch
https://git.kernel.org/stable/c/c12d570d71920903a1a0468b7d13b085203d0c93 Patch
https://cert-portal.siemens.com/productcert/html/ssa-019113.html
https://cert-portal.siemens.com/productcert/html/ssa-082556.html

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Source: NIST National Vulnerability Database (record CVE-2026-23351), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.