CVE-2026-80784: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: fix memory leak from alloc-during-teardown race mptcp_pm_destroy() empties msk->pm.anno_list and msk->pm.userspace_pm_local_addr_list under msk->pm.lock during socket teardown, dropping the lock between the two. A concurrent userspace PM genl ANNOUNCE on the same msk holds a sock reference via mptcp_token_get_sock() and, in mptcp_pm_nl_announce_doit(), calls mptcp_userspace_pm_append_new_local_addr() and mptcp_pm_announced_alloc(). Both take msk->pm.lock briefly to add to their respective lists. Because the genl handler holds a sock reference, mptcp_pm_destroy() may run on the same msk via mptcp_disconnect(), which invokes mptcp_destroy_common() without dropping the sock refcount, before the handler completes. If the lock acquisitions interleave such that mptcp_pm_destroy() empties a list first, the later alloc adds its entry to a list head that nothing else iterates for this msk, and the entry leaks. kmemleak reports both mptcp_pm_add_addr objects (from mptcp_pm_announced_alloc()) and mptcp_pm_addr_entry objects (from mptcp_userspace_pm_append_new_local_addr()) under sustained concurrent ANNOUNCE + close load against the userspace PM. Add an MPTCP_PM_DESTROYING bit in msk->pm.status, set by mptcp_pm_destroy() under pm.lock before the lists are emptied and checked under pm.lock by the alloc paths. Either the alloc takes pm.lock first, in which case its entry is on the list when mptcp_pm_destroy() frees it; or mptcp_pm_destroy() takes pm.lock first, in which case the later alloc observes the bit and refuses. Found by an MPTCP protocol-flow harness extending BRF (arXiv:2305.08782).

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 9ab4807c84a4aacfc9b4f79cc81254035e0ec361, < f48341830e4202db3fe884b819b2db6740f0537d; >= 9ab4807c84a4aacfc9b4f79cc81254035e0ec361, < bb32e9a6a9a9f99eeda16c4efe443400f3e43892; >= 9ab4807c84a4aacfc9b4f79cc81254035e0ec361, < b2a0b55bf613bd3e81ed26a847b0f6b8e6b7f804; >= 9ab4807c84a4aacfc9b4f79cc81254035e0ec361, < 9fe5eebb664ecdba88f3fde18062d94b1d1c465f; >= 9ab4807c84a4aacfc9b4f79cc81254035e0ec361, < 6c290915a03fc8228b473641025cf762b256dbd2; >= 9ab4807c84a4aacfc9b4f79cc81254035e0ec361, < efc33b5102ff859bacd390a5f30112d8e0c084c0
Linux	Linux	5.19

References

Timeline

Published: Sep 4, 2026
Last Modified: Sep 4, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-80784?

In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: fix memory leak from alloc-during-teardown race mptcp_pm_destroy() empties msk->pm.anno_list and msk->pm.userspace_pm_local_addr_list under msk->pm.lock during socket teardown, dropping the lock between the two. A concurrent userspace PM genl ANNOUNCE on the same msk holds a sock reference via mptcp_token_get_sock() and, in mptcp_pm_nl_announce_doit(), calls mptcp_userspace_pm_append_new_local_addr() and mptcp_pm_announced_alloc(). Both take msk->pm.lock briefly to add to their respective lists. Because the genl handler holds a sock reference, mptcp_pm_destroy() may run on the same msk via mptcp_disconnect(), which invokes mptcp_destroy_common() without dropping the sock refcount, before the handler completes. If the lock acquisitions interleave such that mptcp_pm_destroy() empties a list first, the later alloc adds its entry to a list head that nothing else iterates for this msk, and the entry leaks. kmemleak reports both mptcp_pm_add_addr objects (from mptcp_pm_announced_alloc()) and mptcp_pm_addr_entry objects (from mptcp_userspace_pm_append_new_local_addr()) under sustained concurrent ANNOUNCE + close load against the userspace PM. Add an MPTCP_PM_DESTROYING bit in msk->pm.status, set by mptcp_pm_destroy() under pm.lock before the lists are emptied and checked under pm.lock by the alloc paths. Either the alloc takes pm.lock first, in which case its entry is on the list when mptcp_pm_destroy() frees it; or mptcp_pm_destroy() takes pm.lock first, in which case the later alloc observes the bit and refuses. Found by an MPTCP protocol-flow harness extending BRF (arXiv:2305.08782).

How severe is CVE-2026-80784?

Severity scoring for CVE-2026-80784 is pending analysis.

How do I fix CVE-2026-80784?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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