CVE-2026-77641 json
tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails.
published 2026-08-20 2 mo ago modified 2026-10-18 21 d ago also EUVD-2026-63658
- cvss
- 6.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 29%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- torproject Tor 0.4.9.9
- tor Debian 14, Debian 12 0.4.9.9-1
- tor Debian 13 0.4.9.11-0+deb13u1
debian advisories DEBIAN-CVE-2026-77641
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 2 mo ago
Exploit prediction
0.35% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H |
| NVD | 3.1 | 8.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H |
Affected products
- torproject Tor
Classification
- Weakness
-
- CWE-252 Unchecked Return Value
References
-
gitlab.torproject.org
/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog
release-notes, vendor-advisory
Sources
- CVE List CVE-2026-77641
- NVD CVE-2026-77641
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.