CVE-2026-77641
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 9% of all known CVEs.
References
Related Vulnerabilities
Other CWE-252 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2005-4360 | High | 7.8 | 87% | - | - |
| CVE-2007-3798 | Critical | 9.8 | 70% | - | Fix |
| CVE-2010-0211 | Critical | 9.8 | 28% | - | Fix |
| CVE-2022-23626 | High | 8.5 | 9.9% | - | Fix |
| CVE-2019-10902 | High | 7.5 | 4.0% | - | - |
| CVE-2018-20216 | High | 7.5 | 3.9% | - | Fix |
Common questions
How do I fix CVE-2026-77641?
Upgrade tor on debian 12 to 0.4.9.9-1 or later.
Is CVE-2026-77641 being actively exploited?
Not that we know of. CVE-2026-77641 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.19% is the estimated probability that it will be exploited in the next 30 days. That is higher than 9% of all scored CVEs.
How severe is CVE-2026-77641?
CVE-2026-77641 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-77641 affect?
Published advisories record a fix for tor (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-27.