CVE-2026-4965
Published: 27 March 2026
Summary
CVE-2026-4965 is a medium-severity Code Injection (CWE-94) vulnerability. Its CVSS base score is 6.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 7.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
This vulnerability is AI-related — categorised as AI Agent Protocols and Integrations; in the LLM/Generative AI Risks risk domain.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-4965 is a code injection vulnerability stemming from an incomplete fix for CVE-2025-6101 in the letta-ai letta framework version 0.16.4. It affects the resolve_type function within the file letta/functions/ast_parsers.py, where improper neutralization of directives in dynamically evaluated code (classified under CWE-94 and CWE-95) allows malicious input to be processed unsafely. The issue carries a CVSS v3.1 base score of 7.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L), indicating high severity due to its network accessibility and lack of prerequisites.
Remote attackers can exploit this vulnerability without authentication or user interaction by manipulating inputs to the affected function, potentially leading to arbitrary code execution or directive injection during dynamic code evaluation. Successful exploitation grants low-level impacts on confidentiality, integrity, and availability, enabling data leakage, modification of application state, or denial of service within the letta framework's parsing context.
Advisories from VulDB (ctiid.353842, id.353842, submit.777654) document the issue, with a public exploit available via a GitHub Gist (https://gist.github.com/YLChen-007/fc09bc447a73bba526c1642d9ce73ca5). No patches or vendor responses are reported, as the letta-ai team was contacted early but did not reply; security practitioners should avoid version 0.16.4 and monitor for updates.
The exploit's public availability increases the risk of active exploitation, particularly in environments using letta-ai for AI-related dynamic code processing.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16736
Vulnerability details
A vulnerability was detected in letta-ai letta 0.16.4. This issue affects the function resolve_type of the file letta/functions/ast_parsers.py of the component Incomplete Fix CVE-2025-6101. Performing a manipulation results in improper neutralization of directives in dynamically evaluated code. The attack can…
more
be initiated remotely. The exploit is now public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
- CWE(s)
AI Security AnalysisAI
- AI Category
- AI Agent Protocols and Integrations
- Risk Domain
- LLM/Generative AI Risks
- OWASP Top 10 for LLMs 2025
- None mapped
- Classification Reason
- Matched keywords: ai
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated code injection (CWE-94/95) in Python dynamic evaluation directly enables T1190 (Exploit Public-Facing Application) for initial access and T1059.006 (Python) for arbitrary code execution.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely remediation of the specific code injection flaw in letta 0.16.4's resolve_type function via patches or compensating controls.
Mandates validation of inputs to the ast_parsers.py function to neutralize malicious directives before dynamic code evaluation.
Implements memory protections like non-executable regions to mitigate arbitrary code execution even if injection succeeds.