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Fencer Vulns
high 7.0

CVE-2026-77584 json

Tor before 0.4.9.10 did not reject a CONFLUX_LINK cell that arrives on a circuit which already has attached streams.

published 2026-08-20 2 mo ago modified 2026-10-18 21 d ago also EUVD-2026-63591

cvss
7.0
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 16%
public exploits
0
none known

Summary

Tor before 0.4.9.10 did not reject a CONFLUX_LINK cell that arrives on a circuit which already has attached streams. A malicious client could send a RELAY_COMMAND_BEGIN before the CONFLUX_LINK on the same circuit, attaching an exit stream that would later end up orphan leaving a dangling circuit back-pointer and a use-after-free (UAF) when the circuit is freed. This is TROVE-2026-025.

Patch / fix

  • torproject Tor 0.4.9.10
  • 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-2026-77584

  • 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-2026-77584 updated cvss 7.0

tor: Tor: Use-after-free vulnerability via CONFLUX_LINK cell handling

  • 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
partial
Assessed
2 mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L
NVD 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Affected products

  • torproject Tor

Classification

Weakness
  • CWE-821 Incorrect 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.