Invia #777654: letta-ai letta 0.16.4 CWE-95

# Technical Details
A Remote Code Execution (RCE) vulnerability exists via eval() injection in the type annotation coercion mechanism of Letta. This is an incomplete fix for CVE-2025-6101.

The patch for CVE-2025-6101 introduced a safe AST-based type resolver but kept an eval() fallback behind an allow_unsafe_eval flag. Although this flag defaults to False in the resolve_type() signature in letta/functions/ast_parsers.py (lines 55-86), it is hardcoded to True in the sandbox execution paths that call it. When a tool is executed, Letta coerces JSON arguments into Python types by evaluating their type annotations. An attacker can provide a malicious Python expression as a type annotation that bypasses the AST resolver and triggers the eval() fallback.

# Vulnerable Code
File: letta/functions/ast_parsers.py (lines 55-86)
Method: resolve_type()
Why: Uses eval(annotation, python_types) when allow_unsafe_eval=True. The python_types namespace includes vars(builtins), providing access to dangerous functions like __import__.

File: letta/functions/helpers.py (in process_tool_arguments)
Why: Calls resolve_type with allow_unsafe_eval=True hardcoded.

# Reproduction
1. Deploy Letta v0.16.4.
2. Define a tool with a malicious type annotation:
Example: def pxc(cmd: '__import__("os").popen("id").read()'): pass
3. Submit the tool and trigger its execution via POST /v1/tools/run.
4. The server evaluates the annotation during type coercion, executing the injected code.

# Impact
- Full Remote Code Execution (RCE) on the server.
- Unauthenticated access to the underlying OS.
- Potential for full system compromise.

• Fonte: ⚠️ https://gist.github.com/YLChen-007/fc09bc447a73bba526c1642d9ce73ca5
• Utente: Eric-z (UID 95890)
• Sottomissione: 11/03/2026 14:45 (7 mesi fa)
• Moderazione: 27/03/2026 09:23 (16 days later)
• Stato: Accettato
• Voce VulDB: 353842 [letta-ai letta 0.16.4 Incomplete Fix CVE-2025-6101 ast_parsers.py resolve_type Esecuzione di codice remoto]
• Punti: 20