Boringproxy, up to version 0.10.0, allows an authenticated low‑privileged user to inject arbitrary lines into the SSH authorized_keys file by supplying a percent‑encoded newline character in the domain parameter of the tunnel creation endpoint. This injection permits the attacker to add an unrestricted public key, creating persistent shell access; the attacker can then read cleartext credentials from the database file, exposing user tokens, tunnel private keys, and TLS certificates.

The Boringproxy open‑source proxy, version 0.10.0 and earlier, is affected.

This vulnerability carries a CVSS score of 8.5, indicating high severity. The EPSS score is not available, so the current exploitation probability is unknown, and the KEV catalog does not list it. An attacker must first authenticate as a low‑privileged user with tunnel‑creation rights; by inserting a percent‑encoded newline (%0A) into the domain parameter of the tunnel creation endpoint, the attacker can inject arbitrary lines into the SSH authorized_keys file, thereby creating an unrestricted public‑key entry that yields persistent shell access. The attacker can then read cleartext credentials from the database, exposing all user tokens, tunnel private keys, and TLS certificates.