Related Vulnerabilities: CVE-2021-34548  

A security issue has been found in Tor before version 0.4.5.9. Relays could spoof RELAY_END or RELAY_RESOLVED cell on half-closed streams because clients failed to validate which hop sent these cells. This would allow a relay on a circuit to end a stream that wasn't actually built with it.

Severity Medium

Remote Yes

Type Insufficient validation

Description

A security issue has been found in Tor before version 0.4.5.9. Relays could spoof RELAY_END or RELAY_RESOLVED cell on half-closed streams because clients failed to validate which hop sent these cells. This would allow a relay on a circuit to end a stream that wasn't actually built with it.

AVG-2075 tor 0.4.5.8-2 0.4.5.9-1 Medium Fixed

https://blog.torproject.org/node/2041
https://gitlab.torproject.org/tpo/core/tor/-/issues/40389
https://gitlab.torproject.org/tpo/core/tor/-/commit/adb248b6d6e0779719e6b873ee12a1e22fa390f4