CVE-2026-77641

NULL Write After Free in Tor Relay Leading to Crash

Published Aug 20, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title NULL Write After Free in Tor Relay Leading to Crash
Type Values Removed Values Added
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.
First Time appeared Torproject
Torproject tor
Weaknesses CWE-252
CPEs cpe:2.3:a:torproject:tor:*:*:*:*:*:*:*:*
Vendors & Products Torproject
Torproject tor
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Aug 27, 2026, 4:06 PM
Reserved
Aug 20, 2026, 9:09 PM
Status
Analyzed
Published
Aug 20, 2026, 9:17 PM
Modified
Oct 18, 2026, 8:10 PM