9

CVE-2026-77638: torproject tor Race Condition

CVSS: 9.0v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-77638DEBIAN-CVE-2026-77638
Published 20-08-2026Last modified 27-08-2026
Open JSON

Vulnerability summary

CVE-2026-77638 is a critical (CVSS 9.0) Race Condition vulnerability in torproject tor. EPSS estimates a 0.30% chance of exploitation in the next 30 days, higher than 21.1% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.0/10
010
Critical · v3.1 (NVD)
EPSS score
0.30%
0%100%
Low · +0.11 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 2
MGASA-2026-0382OPENSUSE-SU-2026:11590-1OPENSUSE-SU-2026:21660-1

Timeline

  1. 20-08-2026
    PublishedVulnerability first disclosed.
  2. 27-08-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.30%

Chance of exploitation in the next 30 days

Percentile

21%

Versus all other CVEs

30-day change

+0.11 pp

From 0.19% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.30%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Debian1 product
  • tor< 0.4.9.11-0+deb12u1 | < 0.4.9.11-0+deb13u1 | < 0.4.9.11-1
Torproject1 product
  • tor≥ 0.3.5.3-alpha, < 0.4.9.11 | < 0.4.9.11
Ubuntu1 product
  • torAll versions (No fix recorded)

3 vendors · 3 products

References

5 links