CVE-2025-21706: Linux kernel · mptcp: pm: only set fullmesh for subflow endp
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 10 Nov 2026, 14:48 UTC
Rated Low by Threat Radar's AI analysis · No CVSS score from NVD or the CNA
Thin evidence
One scorer or noneExploitation evidence
Disclosed: evidence found.
CVE published 27 Feb 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 10 Nov 2026.
What to do
AI-suggested
A fix has been implemented in the Linux kernel to restrict the 'fullmesh' flag setting to subflow endpoints only. Users should update to a Linux kernel version that includes this fix.
Description
A vulnerability in the Linux kernel's Multipath TCP (MPTCP) path manager allowed the 'fullmesh' flag to be set on implicit endpoints, which was not intended. This issue was identified by syzbot and triggered kernel warnings. The flaw involved the set_flags() hook being overly permissive, potentially causing unexpected behavior in subflow endpoint management.
References
- git.kernel.org/stable/c/22b0734c9401a74ed4ebd9e8ef0da33e493852eb (opens in a new tab)
- git.kernel.org/stable/c/de3b8d41d2547452c4cafb146d003fa4689fbaf2 (opens in a new tab)
- git.kernel.org/stable/c/8ac344cbd84fda75e05e1f445f7f8fb24dc175e1 (opens in a new tab)
- git.kernel.org/stable/c/9e3d61620a3cd033319553b980ff3a350adbe1bc (opens in a new tab)
- git.kernel.org/stable/c/1bb0d1348546ad059f55c93def34e67cb2a034a6 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/03/msg00028.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)