CVE-2026-0685: Server side template inject (SSTI) in Edgewall Genshi Template Engine

Synopsis

Server-side template injection (SSTI) is present in the expression evaluation component of Edgewall Genshi Template Engine version 0.7.9 and earlier. The vulnerability is reachable over the network with no authentication required and no user interaction needed. Successful exploitation gives an attacker full remote code execution on the host running the affected service. No fix has been published yet; HarborGuard is tracking the advisory for patch availability.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Genshi-based service over the network; the CVSS vector specifies AV:N, meaning no local or physical access is needed.

• AuthenticationNot required

  No account or credentials are required; PR:N indicates the attacker can exploit the vulnerability as an anonymous user.

• Victim interactionNot required

  Exploitation requires no action from any user on the target system; UI:N means the attacker operates entirely on their own.

• Attack complexityDetail

  Attack complexity is Low (AC:L), meaning the exploit is reliable and requires no special timing, race conditions, or environment-specific preconditions.

Blast Radius

• A successful attacker achieves remote code execution and can run arbitrary commands under the process identity of the Genshi service.
• Confidentiality impact is High: the attacker reads any data accessible to the process, including environment variables, secrets, configuration files, and in-memory credentials.
• Integrity impact is High: the attacker writes or modifies files, injects data into connected databases, or alters application state on the host.
• Availability impact is High: the attacker crashes the service, exhausts system resources, or deletes critical files, causing a full outage of the affected workload.