# CVE-2026-77641: tor: tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails

CVE-2026-77641 is fixed in tor on 1 platform, first by DEBIAN-CVE-2026-77641, released August 21, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-77641
- Priority: High
- CVSS: 8.2 (high)
- EPSS: 0.0035
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 20, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | tor Debian 12.15 (bookworm) | 0.4.9.9-1 | [DEBIAN-CVE-2026-77641](https://patchblox.com/security/data/fix/linux/debian-cve-2026-77641.md) | Aug 21, 2026 |
| Linux | tor Debian 13.5 (trixie) | 0.4.9.11-0+deb13u1 | [DEBIAN-CVE-2026-77641](https://patchblox.com/security/data/fix/linux/debian-cve-2026-77641.md) | Aug 21, 2026 |
| Linux | tor Debian 14 | 0.4.9.9-1 | [DEBIAN-CVE-2026-77641](https://patchblox.com/security/data/fix/linux/debian-cve-2026-77641.md) | Aug 21, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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