CVE-2026-61756

NVIDIA Megatron Bridge contains a deserialization flaw (CWE-502) in which untrusted serialized data is passed to a deserializer without adequate validation. Per the CVSS vector (local attack vector, low privileges required, no user interaction), exploitation requires an attacker who already has local access or can influence serialized input processed by the tool, such as a training checkpoint or other artifact loaded by the framework. A successful exploit could allow arbitrary code execution, tampering with data, and disclosure of sensitive information in the context of the affected process. Affected users are teams and AI engineering environments running NVIDIA Megatron Bridge (NeMo Megatron Bridge) for LLM training and customization; the available data does not specify affected version ranges. Exploitation status is currently quiet: there is no known public proof of concept, EPSS is only 0.3% over 30 days, and the flaw is not in CISA's KEV catalog.

What to do: Check installed Megatron Bridge versions against NVIDIA's security advisory for CVE-2026-61756 and move to the patched release once NVIDIA specifies it, as no version numbers are included in the available data. As an interim mitigation, restrict deserialization of untrusted artifacts (e.g., checkpoints or model files from untrusted sources), preferring safe formats or restricted-loading options where supported. With no public PoC, low EPSS, and no KEV listing, patching can follow normal maintenance cycles, but prioritize environments where untrusted checkpoints are loaded.