CVE-2026-43624: F5-TTS 1.1.20 Path Traversal via finetune_gradio.py create_data_project()

Synopsis

Path traversal vulnerability in F5-TTS (versions up to and including 1.1.20) allows unauthenticated attackers to write arbitrary files anywhere on the host filesystem writable by the server process. The flaw lives in the finetune Gradio handler's create_data_project() function, which passes unsanitized user-supplied project names directly to os.path.join() without checking that the resulting path stays inside the intended directory. Exploitation requires only a network connection and no credentials, and enables an attacker to write attacker-controlled JSON content to arbitrary filesystem paths. A patched-image rebuild at commit 2f53ded68e5f69e248ceb200a51ef4d1dc647936 is available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The Gradio HTTP endpoint is exposed over the network, so an attacker must be able to reach the service on its listening port.

• AuthenticationNot required

  No credentials or session token are needed; the vulnerable handler accepts unauthenticated requests.

• Victim interactionNot required

  The attack is fully server-side; no user action or social engineering is required.

• Attack complexityDetail

  Exploitation is reliable and condition-free: the attacker supplies a crafted project-name string in a single request with no race conditions or environmental prerequisites.

Blast Radius

• Writes attacker-controlled JSON files to any filesystem path writable by the server process, including sensitive configuration directories.
• Creates arbitrary directories on the host, enabling staging areas for follow-on payloads or overwriting application config files.
• Degrades service availability in a limited way by corrupting files or filling filesystem paths the application depends on (integrity impact rated HIGH, availability impact rated LOW).