CVE-2026-61754

CVE-2026-61754 is a deserialization of untrusted data flaw (CWE-502) in NVIDIA Megatron Bridge, the NVIDIA library for building and post-training large language models within the NeMo/Megatron ecosystem. The vulnerability occurs when the software deserializes attacker-controlled serialized data, with the CVSS vector (AV:L/PR:L/UI:N) indicating exploitation requires local or low-privileged access and no user interaction, consistent with loading untrusted artifacts such as serialized checkpoints into a training or post-training workflow. A successful attacker could achieve arbitrary code execution, tampering of data, and disclosure of sensitive information in the context of the affected process. Anyone running NVIDIA Megatron Bridge is potentially affected; the published data does not specify which versions are vulnerable, so users should consult NVIDIA's advisory for exact affected and fixed versions. Exploitation status is quiet so far: it is not in CISA's KEV, no public proof-of-concept is known, and EPSS assigns only a 0.3% probability of exploitation within 30 days.

What to do: Check the NVIDIA PSIRT bulletin for CVE-2026-61754 to identify affected versions and upgrade Megatron Bridge to the fixed release once published. In the meantime, restrict deserialization to trusted, internally produced checkpoints and serialized files, and limit which accounts or service contexts can load untrusted artifacts into NeMo/Megatron pipelines. Teams running shared or multi-user training environments should treat checkpoint ingestion as an untrusted-input surface until patched.