Bug 2482542 (CVE-2026-46170)

Summary: CVE-2026-46170 kernel: mptcp: pm: ADD_ADDR rtx: free sk if last
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Multipath TCP (MPTCP) implementation. When an ADD_ADDR message is retransmitted, an issue in socket (sk) reference counting can prevent the socket from being properly freed. This improper resource management may lead to a Denial of Service (DoS) condition, where the system could become unresponsive due to indefinite waiting during timer synchronization.
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Description OSIDB Bzimport 2026-05-28 11:02:27 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mptcp: pm: ADD_ADDR rtx: free sk if last

When an ADD_ADDR is retransmitted, the sk is held in sk_reset_timer(),
and released at the end.

If at that moment, it was the last reference being held, the sk would
not be freed. sock_put() should then be called instead of __sock_put().

But that's not enough: if it is the last reference, sock_put() will call
sk_free(), which will end up calling sk_stop_timer_sync() on the same
timer, and waiting indefinitely to finish. So it is needed to mark that
the timer is done at the end of the timer handler when it has not been
rescheduled, not to call sk_stop_timer_sync() on "itself".
Comment 1 Keith Grant 2026-05-28 15:07:54 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026052827-CVE-2026-46170-b7ab@gregkh/T