CVE-2026-97566mptcp: pm: kernel: drop pending ADD_ADDR when removing ID0

Official description

In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: kernel: drop pending ADD_ADDR when removing ID0 The in-kernel MPTCP path manager can leave a stale ADD_ADDR announcement entry alive when removing the id 0 endpoint. This happens because the id 0 removal path does not tear down pending announcements, unlike the non-zero id path. When the PM later reselects id 0 after adding another signal endpoint, it finds the stale anno_list entry and hits WARN_ON_ONCE(mptcp_pm_is_kernel()) in mptcp_pm_announced_alloc(). Root cause: asymmetry between removal paths. - Non-zero id path: mptcp_nl_remove_subflow_and_signal_addr() calls mptcp_pm_remove_announced() to clean up. - Id 0 path: mptcp_nl_remove_id_zero_address() skips cleanup entirely. Fix by making the id 0 path symmetric: call mptcp_pm_announced_remove() and decrement add_addr_signaled before queuing the RM_ADDR. Subtle detail: signal endpoints are stored in anno_list with port 0, but msk_local carries the connection's local port. In other words, entries linked to ID0 paths should have port == 0. A follow-up patch will ensure that. mptcp_pm_announced_remove() uses use_port=true for comparison. So clear the port before the lookup.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4af59a98aead422a152d805a89586dbb65616fc8
• https://git.kernel.org/stable/c/189d60057e5f3d6a62e3d71a3cc428c9150bc14f
• https://git.kernel.org/stable/c/bacf23e7c9876c9f4170166b3597cb22ea3ed39b
• https://git.kernel.org/stable/c/d4a67a880654e1bfe318a31bea0bdbb026a09ade
• https://git.kernel.org/stable/c/545616b4e7325be3c61fc082538cb06d14f7b1db
• https://git.kernel.org/stable/c/2ac7d6e620764f1fc79eb4edd3610a7a661981ca