CVE-2026-77642 Memory corruption in Tor

High 7.5 Published 20 Aug 2026 Updated 27 Aug 2026

An out-of-bounds write in Tor allows attackers to potentially execute code or cause denial of service, primarily affecting directory authorities.

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

What is CVE-2026-77642?

CVE-2026-77642 is a high-severity memory corruption 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 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached signature with unexpected signature digest type. Impact is minor for most Tor roles, but potentially major for directory authorities. This is TROVE-2026-019.

Weakness: CWE-787

Which versions are affected by CVE-2026-77642?

It affects 1 product.

Products include Torproject Tor.

How do I fix CVE-2026-77642?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-77642 being exploited?

There is no known exploitation of CVE-2026-77642 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2026-77642, GHSA-36cc-rhpv-jrxc, UBUNTU-CVE-2026-77642.