CVE-2026-97568: Linux kernel · mptcp: syncookies: remember the request backup flag
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 26 Oct 2026, 12:55 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 25 Sep 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
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix has been implemented in the Linux kernel to address this issue by correctly using the request backup flag bit. Users should apply the updated kernel versions that include this fix. Patch status is not explicitly stated, but the vulnerability is described as resolved in the specified versions.
Description
A vulnerability in the Linux kernel's multipath TCP (mptcp) syncookies implementation was resolved by properly handling the request backup flag. The issue involved using an uninitialized bit in the subflow_ulp_clone() function, which has been corrected by using a single bit from the mptcp_subflow_request_sock structure instead of extending the join_entry structure.
References
- ubuntu.com/security/CVE-2026-97568 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-97568 (opens in a new tab)
- git.kernel.org/stable/c/61178d0b85b4b1b53e78b06e89d018d22d102f88 (opens in a new tab)
- git.kernel.org/stable/c/b76c0e28b392620dfbaf92cdeedbf115820b44cb (opens in a new tab)
- git.kernel.org/stable/c/06d649f9cd03a9f8e768a658b20acf8d2c8022e0 (opens in a new tab)
- git.kernel.org/stable/c/00b2bd518911e0daab00f4749cce68c191ccebb4 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-97568 (opens in a new tab)
- git.kernel.org/stable/c/1668b34452009d27be3262646de748a3e48ffd51 (opens in a new tab)
- git.kernel.org/stable/c/360d99258a6402cb8e49771460944f19f04d25b7 (opens in a new tab)
- git.kernel.org/stable/c/b138e7dc719f0a3949de8bb6500b8cf1604eea06 (opens in a new tab)
- git.kernel.org/stable/c/c97fa2c7ada82d4cac1c6c00643238dc4c462f15 (opens in a new tab)