Vulnerability · Published Aug 20, 2026 · Assigned by mitre
CVE-2026-77641
Medium 6.5
In plain English
A medium-severity security flaw in Tor from torproject. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | tor | 0.4.9.9-1 | DEBIAN-CVE-2026-77641 |
| Debian:13 | tor | 0.4.9.11-0+deb13u1 | DEBIAN-CVE-2026-77641 |
| Debian:14 | tor | 0.4.9.9-1 | DEBIAN-CVE-2026-77641 |
| Ubuntu:22.04:LTS | tor | no fix listed | UBUNTU-CVE-2026-77641 |
| Ubuntu:24.04:LTS | tor | no fix listed | UBUNTU-CVE-2026-77641 |
| Ubuntu:26.04:LTS | tor | no fix listed | UBUNTU-CVE-2026-77641 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| torproject | Tor | 0.4.8.1-alpha – before 0.4.9.9 |
Weakness: CWE-252 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H