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Fencer Vulns
high 8.9

CVE-2026-77638 json

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 (imperson…

published 2026-08-20 2 mo ago modified 2026-10-18 21 d ago also EUVD-2026-63647

cvss
8.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

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.

Patch / fix

  • torproject Tor 0.4.9.11
  • tor Debian 12 0.4.9.11-0+deb12u1
  • tor Debian 13 0.4.9.11-0+deb13u1
  • tor Debian 14 0.4.9.11-1

debian advisories DEBIAN-CVE-2026-77638

  • tor openSUSE Leap 16.0 0.4.9.11-bp160.1.1
  • tor openSUSE Tumbleweed 0.4.9.11-1.1

opensuse advisories openSUSE-SU-2026:21660-1openSUSE-SU-2026:11590-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-77638 updated cvss 8.9

tor: Tor: Onion Service Impersonation via Race Condition

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 mo ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
NVD 3.1 9.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

  • torproject Tor

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.