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VulnerabilityPublished Updated

CVE-2026-43198: Linux kernel · tcp: fix potential race in tcp_v6_syn_recv_sock()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in fe89b2f05b854847784f91127319172945c1fadd : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 14:18 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 22% 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 can 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 fe89b2f05b854847784f91127319172945c1fadd, dad1fe7db6c6519138430ac8f5e589c18f83bfc9, cd644e6dc72eec8d9d988717ea1c54f8668ded69 +5
CVSS:3.1/AV:N/AC:L/PR:N/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
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < fe89b2f05b854847784f91127319172945c1fadd
Fixed in
  • fe89b2f05b854847784f91127319172945c1fadd
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < dad1fe7db6c6519138430ac8f5e589c18f83bfc9
Fixed in
  • dad1fe7db6c6519138430ac8f5e589c18f83bfc9
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < cd644e6dc72eec8d9d988717ea1c54f8668ded69
Fixed in
  • cd644e6dc72eec8d9d988717ea1c54f8668ded69
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < aef4a9ae95d1bc4f7897065011e6261026719aeb
Fixed in
  • aef4a9ae95d1bc4f7897065011e6261026719aeb
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < a7e761ba55efaa9c49e0afdd304bb78167af3429
Fixed in
  • a7e761ba55efaa9c49e0afdd304bb78167af3429
LinuxLinuxAffected
  • ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 7178e2a8027423b2af17ab95df73a749a5b72e5b
Fixed in
  • 7178e2a8027423b2af17ab95df73a749a5b72e5b

Description

In the Linux kernel, the following vulnerability has been resolved: tcp: fix potential race in tcp_v6_syn_recv_sock() Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context.

References

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