CVE-2026-77587 Use after free in Tor

Medium 5.9 Published 20 Aug 2026 Updated 25 Aug 2026

A malicious exit node can crash a Tor client by triggering a use-after-free in conflux object handling.

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

What is CVE-2026-77587?

CVE-2026-77587 is a medium-severity use after free vulnerability in torproject Tor, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Tor before 0.4.9.11 is prone to a use-after-free (and potential double free) of a conflux object when a recovery leg revives a conflux set whose last linked leg has already been closed. A malicious exit node could use this to crash a client. This is TROVE-2026-026.

Weakness: CWE-416, CWE-911

Which versions are affected by CVE-2026-77587?

It affects 1 product.

Products include Torproject Tor.

How do I fix CVE-2026-77587?

Upgrade to a fixed version.

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-2026-77587 being exploited?

There is no known exploitation of CVE-2026-77587 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2026-77587, GHSA-9mf5-x83c-fg2x, UBUNTU-CVE-2026-77587.