CVE-2026-61771

NVIDIA Megatron Bridge contains a deserialization-of-untrusted-data flaw (CWE-502) that can allow code execution, data tampering, and information disclosure when exploited. It is triggered when the software deserializes attacker-controlled or otherwise untrusted serialized data; the CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N) indicates a local attack surface requiring only low privileges and no user interaction. An attacker who can get Megatron Bridge to process their serialized data gains code execution with the privileges of the affected process, plus the ability to alter data and expose sensitive information. Anyone running NVIDIA Megatron Bridge in LLM training or post-training pipelines is potentially affected, though the data provided does not specify affected version ranges. There is no known public proof-of-concept, the flaw is not in CISA KEV, and EPSS puts 30-day exploitation probability at about 0.2%, so no active exploitation is currently known.

What to do: Check the NVIDIA security advisory for this CVE to identify affected and fixed versions, and upgrade Megatron Bridge to a patched release. In the meantime, audit any workflows that deserialize untrusted or third-party-supplied serialized data (such as externally sourced model or checkpoint files) with Megatron Bridge, and run training jobs with least-privilege credentials to limit blast radius. Monitor NVIDIA channels for a published PoC or signs of in-the-wild exploitation.