CVE-2026-43029: Linux kernel · mptcp: fix soft lockup in mptcp_recvmsg()
Source GCVE Database
Not known to be exploited · CVSS 7.5 High.
Data as of 27 Oct 2026, 01:02 UTC
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 1 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
AI-suggested
A fix for this vulnerability has been implemented in the Linux kernel by adding tracking of the last peeked skb in mptcp_recvmsg(), preventing the soft lockup. Users should apply the official kernel updates that include this fix once available. Since this is a kernel-level issue, updating to a fixed kernel version is the recommended remediation. Patch status is not explicitly confirmed in the provided data; users should consult the Linux kernel vendor advisory or distribution security updates for the fixed versions.
Description
A high-severity vulnerability in the Linux kernel's Multipath TCP (mptcp) implementation causes a soft lockup in the mptcp_recvmsg() function when receiving data with MSG_PEEK and MSG_WAITALL flags. The issue arises because the socket buffer (skb) is not removed from the receive queue, causing the kernel to enter an infinite loop waiting for data. This flaw was reported by syzbot and fixed by adding a mechanism to track the last peeked skb, allowing proper waiting behavior and preventing the lockup.
References
- nvd.nist.gov/vuln/detail/CVE-2026-43029 (opens in a new tab)
- git.kernel.org/stable/c/58b58b9ba89c43914eea90c18928e51852d10c24 (opens in a new tab)
- git.kernel.org/stable/c/5dd8025a49c268ab6b94d978532af3ad341132a7 (opens in a new tab)
- git.kernel.org/stable/c/de3c248d1b69eaefa2d5b3da4005936dcf590f1b (opens in a new tab)