# CVE-2026-77642 — torproject Tor

> As of 2026-08-20, CVE-2026-77642 is a HIGH-severity vulnerability in torproject Tor, CVSS v3.1 7.5, EPSS 0.1% (9.4th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-77642 as of 2026-08-20; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-20

## What is CVE-2026-77642?

tor before 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached signature with unexpected signature digest type. Impact is minor for most Tor roles, but potentially major for directory authorities. This is TROVE-2026-019.

The record classifies CVE-2026-77642 under weakness class [CWE-787](https://intel.threadlinqs.com/cwe/CWE-787). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 46 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 9.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.1/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-20

## Is CVE-2026-77642 being exploited?

It currently carries a trending score of 32 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **torproject**: Tor

## How to fix CVE-2026-77642

No vendor patch reference has been recorded for CVE-2026-77642 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-77642

No threat campaign in the Threadlinqs corpus currently references CVE-2026-77642, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-08-22.

**Other references**

- [gitlab.torproject.org](https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-77642
Full detection coverage and IOCs for threats exploiting CVE-2026-77642 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp