CVE-2026-61776

NVIDIA Megatron Bridge, NVIDIA's open-source framework for training and post-training large language models, contains a deserialization-of-untrusted-data vulnerability (CWE-502). The flaw is triggered when the framework deserializes untrusted serialized input — the CVSS vector (AV:L/PR:L/UI:N) indicates a local, low-privilege context, which in an LLM training framework typically means loading crafted checkpoints or other serialized artifacts rather than a network-facing service. A successful exploit could allow the attacker to execute arbitrary code in the training environment, tamper with data (including training artifacts), and disclose sensitive information, consistent with the high confidentiality, integrity, and impact scores. Anyone running NVIDIA Megatron Bridge in training or fine-tuning pipelines — particularly environments that ingest checkpoints or serialized data from external or less-trusted sources — is potentially affected. Exploitation status: no public proof-of-concept, no known in-the-wild exploitation, and the CVE is not in CISA KEV; EPSS estimates only a 0.2% probability of exploitation in the next 30 days.

What to do: Check NVIDIA's security bulletin ([email protected] CNA advisory) for the affected version ranges and upgrade Megatron Bridge to the fixed release it specifies. Until patched, only load checkpoints and serialized artifacts from trusted sources and restrict local access to training environments; note the low current exploitation risk (EPSS 0.2%, not in KEV) but re-check advisories for updated guidance.