CVE-2026-77638 Race condition in Tor
A race condition allows a malicious rendezvous point to impersonate an onion service, enabling man-in-the-middle attacks against Tor clients.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77638?
CVE-2026-77638 is a high-severity 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 race condition where in just the right circumstances a rendezvous point could man-in-the-middle (impersonate) the onion service that the client was trying to reach.
Weakness: CWE-362
Which versions are affected by CVE-2026-77638?
It affects 1 product.
Products include Torproject Tor.
How do I fix CVE-2026-77638?
Upgrade to a fixed version.
Is CVE-2026-77638 being exploited?
There is no known exploitation of CVE-2026-77638 in the wild and no public exploit code.
Other vulnerabilities in torproject Tor
Sources
Also known as DEBIAN-CVE-2026-77638, GHSA-pq38-gw56-4w65, UBUNTU-CVE-2026-77638.