Bug 2439885 (CVE-2026-23169)

Summary: CVE-2026-23169 kernel: Linux kernel: Denial of Service in MPTCP due to a race condition
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's Multipath TCP (MPTCP) implementation. A race condition exists in the mptcp_pm_nl_flush_addrs_doit() function due to improper synchronization when handling network addresses. This flaw could allow a local attacker to trigger system crashes, leading to a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-02-14 17:01:26 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mptcp: fix race in mptcp_pm_nl_flush_addrs_doit()

syzbot and Eulgyu Kim reported crashes in mptcp_pm_nl_get_local_id()
and/or mptcp_pm_nl_is_backup()

Root cause is list_splice_init() in mptcp_pm_nl_flush_addrs_doit()
which is not RCU ready.

list_splice_init_rcu() can not be called here while holding pernet->lock
spinlock.

Many thanks to Eulgyu Kim for providing a repro and testing our patches.
Comment 1 Alexander B 2026-02-16 14:19:09 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026021420-CVE-2026-23169-38ea@gregkh/T