Tor Project 0.4.9.9 Rendezvous Point race condition

Summaryinfo

A vulnerability marked as very critical has been reported in Tor Project Tor. The impacted element is an unknown function of the component Rendezvous Point. Performing a manipulation results in race condition. This vulnerability was named CVE-2026-77638. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Tor Project Tor. It has been classified as very critical. This affects an unknown code of the component Rendezvous Point. The manipulation with an unknown input leads to a race condition vulnerability. CWE is classifying the issue as CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Tor before 0.4.9.11 is prone to a race condition where in just the right circumstances a rendezvous point could man-in-the-middle (impersonate) the onion service that the client was trying to reach.

The advisory is shared at gitlab.torproject.org. This vulnerability is uniquely identified as CVE-2026-77638 since 08/20/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/21/2026).

The vulnerability scanner Nessus provides a plugin with the ID 338660 (Linux Distros Unpatched Vulnerability : CVE-2026-77638), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 0.4.9.11 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (338660). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Project Management Software

Vendor

• Tor Project

Name

• Tor

Version

• 0.4.9.9

License

• open-source

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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