Vulnerability in Torproject Tor
CVE-2026-77638
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.
Vulnerability class: Race Condition
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.9 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L.
EPSS exploit prediction
EPSS: 0.003 (20.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 20th percentile — 20.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.11/ChangeLog (Permissions Required, Release Notes, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-77638?
- CVE-2026-77638 is a high-severity vulnerability in Torproject Tor, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 8.9/10. Published 2026-08-20.
- How severe is CVE-2026-77638?
- High severity. CVSS v3 base score is 8.9 out of 10.