CVE-2026-98586 sctp: hold asoc or transport before mod_timer() in timer handlers

Not scored Published 18 Oct 2026 Updated 19 Oct 2026

A race condition in Linux kernel SCTP timer handlers allows use-after-free, potentially leading to denial of service or code execution.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-98586?

CVE-2026-98586 is an use after free vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

sctp: hold asoc or transport before mod_timer() in timer handlers

Take the association or transport reference before rearming a timer in the timer handlers.

The existing code calls mod_timer() before taking the reference needed by the rearmed timer without holding the sock lock. This creates a race with timer cleanup: if the timer is deleted after mod_timer() returns but before the reference is taken, the cleanup path can drop the timer's reference and destroy the transport or association. The timer handler then takes a reference on the already freed object and eventually drops it, causing a refcount underflow.

Hold the object before mod_timer() and drop the reference if mod_timer() reports that the timer was already pending in timer handlers. Apply the same ordering to the proto-unreachable path, which can rearm a transport timer outside the timer handlers without holding the sock lock.

Which versions are affected by CVE-2026-98586?

How do I fix CVE-2026-98586?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-98586 being exploited?

There is no known exploitation of CVE-2026-98586 in the wild and no public exploit code.

Sources

Also known as AZL-108647, BELL-CVE-2026-98586, DEBIAN-CVE-2026-98586, GHSA-4473-fgjm-w85x, UBUNTU-CVE-2026-98586.