CVE-2026-61778

NVIDIA NeMo Megatron Bridge contains a deserialization-of-untrusted-data vulnerability (CWE-502), in which the framework processes attacker-controlled serialized input without adequate validation. The CVSS vector scores this as a local attack requiring low privileges with no user interaction, meaning it is triggered when a local or low-privileged actor causes the framework to deserialize untrusted data, such as an artifact supplied to a training or loading workflow. A successful exploit could result in arbitrary code execution, tampering with data, and disclosure of sensitive information, each rated high in the CVSS impact metrics. The flaw affects users of NVIDIA's Megatron Bridge LLM training framework; no specific affected or fixed version ranges were provided in the available data. Exploitation is not currently observed: there is no known public proof-of-concept, the flaw is not in CISA's KEV catalog, and EPSS estimates only a 0.2% probability of exploitation in the next 30 days (11th percentile).

What to do: Check NVIDIA's PSIRT advisory for CVE-2026-61778 to identify affected and fixed Megatron Bridge versions and upgrade to the latest patched release. As an interim measure, avoid deserializing checkpoints, data files, or other artifacts from untrusted or unverified sources, and restrict which users can supply serialized inputs to Megatron Bridge training and loading jobs. Monitor NVIDIA's advisory page for follow-up updates, since exploitation risk may grow as the framework is widely used in AI pipelines.