---
id: CVE-2026-87724
title: >-
  Tor before 0.4.9.12 interprets the CC_RESPONSE extension even when CC_REQUEST
  was not sent, which allows remote attackers to cause a denial of service
  (crash) because of corrupted congestion-control state
summary: >-
  Tor before 0.4.9.12 interprets the CC_RESPONSE extension even when CC_REQUEST
  was not sent, which allows remote attackers to cause a denial of service
  (crash) because of corrupted congestion-control state. This is TROVE-2026-032.
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-669
vendor: torprject
product: Tor
affected:
  - Tor >= 0.4.9.3-alpha < 0.4.9.12
published: '2026-09-09'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T19:17:50.287'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-87724'
references:
  - url: >-
      https://gitlab.com/torproject/tor/-/commit/10d4b8ffefa7c00aab2b631ed7e7f15e42cd012d
    label: cve@mitre.org
  - url: 'https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.12/ChangeLog'
    label: cve@mitre.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-87724.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-87724'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-87724'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-09T18:18:26.862750Z'
epss: 0.0026
epssPercentile: 0.18005
ingestedAt: '2026-09-09T02:19:39.649Z'
---

## Overview

Tor before 0.4.9.12 interprets the CC_RESPONSE extension even when CC_REQUEST was not sent, which allows remote attackers to cause a denial of service (crash) because of corrupted congestion-control state. This is TROVE-2026-032.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · updated 2026-09-09 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-87724.json)