CVE-2026-43198: Linux kernel · tcp: fix potential race in tcp_v6_syn_recv_sock()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 3.13.0-215.266 : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 14:05 UTC
- 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.
- Patch
- Available – fixed in 3.13.0-215.266, 4.4.0-1157.163, 4.15.0-1205.220~14.04.1 +113
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 6 May 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-8630-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8633-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8634-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8635-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8636-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8630-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8633-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8645-1 (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: 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
- ubuntu.com/security/CVE-2026-43198 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-43198 (opens in a new tab)
- git.kernel.org/linus/858d2a4f67ff69e645a43487ef7ea7f28f06deae (opens in a new tab)
- ubuntu.com/security/notices/USN-8630-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8633-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8634-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8635-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8636-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8630-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8633-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8631-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8645-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8630-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8636-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8656-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8661-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8630-4 (opens in a new tab)