CVE-2026-80784 - Vulnerability Details

- mptcp: pm: fix memory leak from alloc-during-teardown race

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).

Published: 2026-09-04

Score: n/a

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

In the Linux kernel MPTCP protocol, a race between the socket teardown routine and a concurrent userspace PM announce leaves orphaned list entries in memory. The torn list is populated after cleanup, causing leakage of objects that the kernel never frees. These leaks are reported by the kernel memory‑leak detector as persistent MPTCP pm_addr_entry and pm_add_addr objects, gradually consuming kernel memory.

Affected Systems

All Linux kernel releases that implement MPTCP before the fix are impacted, including both mainline and distribution kernels. The vulnerability applies to systems with MPTCP enabled regardless of the specific distribution, as the bug is in the kernel’s internal state management for PM communication.

Risk and Exploitability

This flaw does not grant code execution or privilege escalation; it simply causes memory leakage, which can result in resource exhaustion and a denial‑of‑service under sustained load. The EPSS score is not available, and the vulnerability is not listed in the CISA KEV catalog. The risk is mitigated by applying the patch that introduces a DESTROYING flag to guard the list updates, or by disabling MPTCP when the patch cannot be applied.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`9ab4807c84a4aacfc9b4f79cc81254035e0ec361`	affected	< f48341830e4202db3fe884b819b2db6740f0537d
`9ab4807c84a4aacfc9b4f79cc81254035e0ec361`	affected	< bb32e9a6a9a9f99eeda16c4efe443400f3e43892
`9ab4807c84a4aacfc9b4f79cc81254035e0ec361`	affected	< b2a0b55bf613bd3e81ed26a847b0f6b8e6b7f804
`9ab4807c84a4aacfc9b4f79cc81254035e0ec361`	affected	< 9fe5eebb664ecdba88f3fde18062d94b1d1c465f
`9ab4807c84a4aacfc9b4f79cc81254035e0ec361`	affected	< 6c290915a03fc8228b473641025cf762b256dbd2
`9ab4807c84a4aacfc9b4f79cc81254035e0ec361`	affected	< efc33b5102ff859bacd390a5f30112d8e0c084c0

Linux

affected

Version	Status	Constraints
`5.19`	affected	—
`0`	unaffected	< 5.19
`6.1.187`	unaffected	≤ 6.1.*
`6.6.154`	unaffected	≤ 6.6.*
`6.12.106`	unaffected	≤ 6.12.*
`6.18.47`	unaffected	≤ 6.18.*
`7.1.11`	unaffected	≤ 7.1.*
`7.2`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[9ab4807c84a4aacfc9b4f79cc81254035e0ec361,f48341830e4202db3fe884b819b2db6740f0537d)`	affected	code_commit	—
`[9ab4807c84a4aacfc9b4f79cc81254035e0ec361,bb32e9a6a9a9f99eeda16c4efe443400f3e43892)`	affected	code_commit	—
`[9ab4807c84a4aacfc9b4f79cc81254035e0ec361,b2a0b55bf613bd3e81ed26a847b0f6b8e6b7f804)`	affected	code_commit	—
`[9ab4807c84a4aacfc9b4f79cc81254035e0ec361,9fe5eebb664ecdba88f3fde18062d94b1d1c465f)`	affected	code_commit	—
`[9ab4807c84a4aacfc9b4f79cc81254035e0ec361,6c290915a03fc8228b473641025cf762b256dbd2)`	affected	code_commit	—
`[9ab4807c84a4aacfc9b4f79cc81254035e0ec361,efc33b5102ff859bacd390a5f30112d8e0c084c0)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`5.19`	affected	generic	—
`[0,5.19)`	unaffected	generic	—
`[6.1.187,6.2.0)`	unaffected	semver	—
`[6.6.154,6.7.0)`	unaffected	semver	—
`[6.12.106,6.13.0)`	unaffected	semver	—
`[6.18.47,6.19.0)`	unaffected	semver	—
`[7.1.11,7.2.0)`	unaffected	semver	—
`[7.2,*]`	unaffected	generic	—

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Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Upgrade the Linux kernel to a version that incorporates the MPTCP DESTROYING flag fix (refer to the commit linked in the advisory).
If an immediate kernel upgrade is not feasible, disable MPTCP or restrict its usage in system configuration to eliminate the race between teardown and userspace PM announce.
After applying the patch or disabling MPTCP, monitor kernel memory pools and use tools such as kmemleak to verify that no orphaned MPTCP pm_addr_entry or pm_add_addr objects remain.

Generated by OpenCVE AI on September 4, 2026 at 17:48 UTC.

Tracking

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Advisories

No advisories yet.

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00173.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/6c290915a03fc8228b473641025cf762b256dbd2
https://git.kernel.org/stable/c/9fe5eebb664ecdba88f3fde18062d94b1d1c465f
https://git.kernel.org/stable/c/b2a0b55bf613bd3e81ed26a847b0f6b8e6b7f804
https://git.kernel.org/stable/c/bb32e9a6a9a9f99eeda16c4efe443400f3e43892
https://git.kernel.org/stable/c/efc33b5102ff859bacd390a5f30112d8e0c084c0
https://git.kernel.org/stable/c/f48341830e4202db3fe884b819b2db6740f0537d

History

Fri, 04 Sep 2026 18:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-362

Fri, 04 Sep 2026 15:30:00 +0000

Type	Values Removed	Values Added
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).
Title		mptcp: pm: fix memory leak from alloc-during-teardown race
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/6c290915a03fc8228b473641025cf762b256dbd2 https://git.kernel.org/stable/c/9fe5eebb664ecdba88f3fde18062d94b1d1c465f https://git.kernel.org/stable/c/b2a0b55bf613bd3e81ed26a847b0f6b8e6b7f804 https://git.kernel.org/stable/c/bb32e9a6a9a9f99eeda16c4efe443400f3e43892 https://git.kernel.org/stable/c/efc33b5102ff859bacd390a5f30112d8e0c084c0 https://git.kernel.org/stable/c/f48341830e4202db3fe884b819b2db6740f0537d

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-09-04T15:12:56.125Z

Updated: 2026-09-04T15:12:56.125Z

Reserved: 2026-08-26T14:34:25.792Z

Link: CVE-2026-80784

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-09-04T16:18:04.333

Modified: 2026-09-04T16:18:04.333

Link: CVE-2026-80784

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-09-04T18:45:02Z

Weaknesses

CWE-362
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Impact

Affected Systems

Risk and Exploitability

Tracking

Subscriptions

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