Executive brief
Tor is anonymity software used by millions to protect their privacy and evade censorship. A bug in how Tor handles network circuit recovery could allow a malicious exit node (an internet relay point) to crash a user's Tor client, disrupting their connection and potentially revealing their real IP address or making them unavailable temporarily.
Technical details
A use-after-free and potential double-free vulnerability exists in Tor's conflux object handling when a recovery leg revives a conflux set whose last linked leg has already been closed. The flaw is in the memory management logic that governs circuit recovery in Tor's conflux (parallel circuits) feature. The attack requires a malicious exit node in the target user's circuit, which is reachable over the network. Successful exploitation crashes the Tor client, causing a denial of service. The vulnerability is fixed in Tor 0.4.9.11 and later versions.
Affected products
- Tor Project Tor before 0.4.9.11
Timeline
- 2026-08-20: disclosed