CVE-2026-23351: Linux kernel · netfilter: nft_set_pipapo: split gc into unlink and reclaim phase
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.15.0-1108.115~20.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 10:12 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1108.115~20.04.1, 5.15.0-1114.123~20.04.1, 5.15.0-1108.117~20.04.1 +78
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 25 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-8277-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8278-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8279-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8289-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8291-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8277-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8291-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8296-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8279-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8291-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8296-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8279-3 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
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").
References
- ubuntu.com/security/CVE-2026-23351 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23351 (opens in a new tab)
- git.kernel.org/linus/9df95785d3d8302f7c066050117b04cd3c2048c2 (opens in a new tab)
- git.kernel.org/stable/c/16f3595c0441d87dfa005c47d8f95be213afaa9e (opens in a new tab)
- git.kernel.org/stable/c/500a50a301ce962b019ab95053ac70264fec2c21 (opens in a new tab)
- git.kernel.org/stable/c/7864c667aed01a58b87ca518a631322cd0ac34c0 (opens in a new tab)
- git.kernel.org/stable/c/9df95785d3d8302f7c066050117b04cd3c2048c2 (opens in a new tab)
- git.kernel.org/stable/c/aff13667708dfa0dce136b8efd81baa9fa6ef261 (opens in a new tab)
- git.kernel.org/stable/c/c12d570d71920903a1a0468b7d13b085203d0c93 (opens in a new tab)
- ubuntu.com/security/notices/USN-8277-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8278-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8279-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8289-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8291-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8277-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8291-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8296-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8279-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8291-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8296-2 (opens in a new tab)