{"id":"CVE-2026-77641","title":"tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails","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 …","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H","cwe":["CWE-252"],"vendor":"torproject","product":"tor","affected":["tor < 0.4.9.9"],"patched":["tor 0.4.9.9"],"published":"2026-08-20","updated":"2026-09-08","sourceUpdated":"2026-09-08T18:23:16.410","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-77641","references":[{"url":"https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog","label":"cve@mitre.org"}],"tags":["nvd"],"epss":0.00202,"epssPercentile":0.10396,"ingestedAt":"2026-09-08T19:08:49.591Z","slug":"CVE-2026-77641","body":"## Overview\n\ntor 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.\n\n## Affected\n\n- `tor < 0.4.9.9`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `tor 0.4.9.9`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}