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VulnerabilityPublished Updated

CVE-2026-43116: Linux kernel · netfilter: ctnetlink: ensure safe access to master conntrack

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in f338ced0473849c9f6ed0b77ca99f1aab5826787 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:18 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in f338ced0473849c9f6ed0b77ca99f1aab5826787, d52fa1fa7440676b8c238037a050ab008c22737f, bffcaad9afdfe45d7fc777397d3b83c1e3ebffe5 +3
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 6 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ c1d10adb4a521de5760112853f42aaeefcec96eb, < f338ced0473849c9f6ed0b77ca99f1aab5826787
Fixed in
  • f338ced0473849c9f6ed0b77ca99f1aab5826787
LinuxLinuxAffected
  • ≥ c1d10adb4a521de5760112853f42aaeefcec96eb, < d52fa1fa7440676b8c238037a050ab008c22737f
Fixed in
  • d52fa1fa7440676b8c238037a050ab008c22737f
LinuxLinuxAffected
  • ≥ c1d10adb4a521de5760112853f42aaeefcec96eb, < bffcaad9afdfe45d7fc777397d3b83c1e3ebffe5
Fixed in
  • bffcaad9afdfe45d7fc777397d3b83c1e3ebffe5
LinuxLinuxAffected
  • ≥ c1d10adb4a521de5760112853f42aaeefcec96eb, < 497f99b26fffdc5635706d1b4811f1ed8ee21a5b
Fixed in
  • 497f99b26fffdc5635706d1b4811f1ed8ee21a5b
LinuxLinuxAffected
  • ≥ c1d10adb4a521de5760112853f42aaeefcec96eb, < 9e1196d27ef496f404c76f7a9d03761142d991c4
Fixed in
  • 9e1196d27ef496f404c76f7a9d03761142d991c4
LinuxLinuxAffected
  • ≥ c1d10adb4a521de5760112853f42aaeefcec96eb, < 5e1c1d22268ae710c238342c8030c21daf298168
Fixed in
  • 5e1c1d22268ae710c238342c8030c21daf298168

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: ensure safe access to master conntrack Holding reference on the expectation is not sufficient, the master conntrack object can just go away, making exp->master invalid. To access exp->master safely: - Grab the nf_conntrack_expect_lock, this gets serialized with clean_from_lists() which also holds this lock when the master conntrack goes away. - Hold reference on master conntrack via nf_conntrack_find_get(). Not so easy since the master tuple to look up for the master conntrack is not available in the existing problematic paths. This patch goes for extending the nf_conntrack_expect_lock section to address this issue for simplicity, in the cases that are described below this is just slightly extending the lock section. The add expectation command already holds a reference to the master conntrack from ctnetlink_create_expect(). However, the delete expectation command needs to grab the spinlock before looking up for the expectation. Expand the existing spinlock section to address this to cover the expectation lookup. Note that, the nf_ct_expect_iterate_net() calls already grabs the spinlock while iterating over the expectation table, which is correct. The get expectation command needs to grab the spinlock to ensure master conntrack does not go away. This also expands the existing spinlock section to cover the expectation lookup too. I needed to move the netlink skb allocation out of the spinlock to keep it GFP_KERNEL. For the expectation events, the IPEXP_DESTROY event is already delivered under the spinlock, just move the delivery of IPEXP_NEW under the spinlock too because the master conntrack event cache is reached through exp->master. While at it, add lockdep notations to help identify what codepaths need to grab the spinlock.

References

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