8.2

CVE-2026-77641: torproject tor Unchecked Return Value

CVSS: 8.2v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-77641DEBIAN-CVE-2026-77641
Published 20-08-2026Last modified 27-08-2026
Open JSON

Vulnerability summary

CVE-2026-77641 is a high (CVSS 8.2) Unchecked Return Value vulnerability in torproject tor. EPSS estimates a 0.35% chance of exploitation in the next 30 days, higher than 27.5% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.2/10
010
High · v3.1 (NVD)
EPSS score
0.35%
0%100%
Low · +0.15 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 1
MGASA-2026-0382

Timeline

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

Description

tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails. The return value of relay_send_command_from_edge() was ignored, so a send failure (which calls circuit_mark_for_close() and removes the leg via cfx_del_leg()) would go undetected, causing the caller to write to the now-freed current leg and resulting in a crash. This is TROVE-2026-017.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.35%

Chance of exploitation in the next 30 days

Percentile

28%

Versus all other CVEs

30-day change

+0.15 pp

From 0.20% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.35%

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< 0.4.9.9-1 | < 0.4.9.11-0+deb13u1
Torproject1 product
  • tor≥ 0.4.8.1-alpha, < 0.4.9.9 | < 0.4.9.9
Ubuntu1 product
  • torAll versions (No fix recorded)

3 vendors · 3 products

References

5 links