CVE-2026-87724 Denial of service in Tor
Remote attackers can crash Tor instances by sending unexpected congestion-control responses, requiring an upgrade to the latest version.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-87724?
CVE-2026-87724 is a medium-severity denial of service vulnerability in torprject Tor, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-669
Which versions are affected by CVE-2026-87724?
Linux distribution packages (1)
tor openSUSE:Tumbleweed | All versions | 0.4.9.13-1.1 |
How do I fix CVE-2026-87724?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-87724 being exploited?
There is no known exploitation of CVE-2026-87724 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-87724, GHSA-c2x3-p37c-phvc, MGASA-2026-0392, UBUNTU-CVE-2026-87724, openSUSE-SU-2026:11909-1.