CVE-2025-33253: 
Python vulnerability analysis and mitigation

CVE-2025-33253 is a deserialization of untrusted data vulnerability (CWE-502) in the NVIDIA NeMo Framework that enables remote code execution when a user is convinced to load a maliciously crafted file. It affects all NeMo versions prior to 2.6.1. The vulnerability was published on February 18, 2026, with NIST initial analysis completed on February 20, 2026. It carries a CVSS v3.1 base score of 7.3 (High) per NVD, and 7.8 (High) per NVIDIA's own CNA scoring (NVD, NVIDIA Advisory).

The root cause is improper deserialization of untrusted data (CWE-502, mapped to CAPEC-586: Object Injection), where the NeMo Framework fails to safely handle externally supplied serialized objects when loading model or configuration files. An attacker crafts a malicious file that, when loaded by a legitimate user running NeMo with low privileges, triggers arbitrary code execution during the deserialization process. The attack vector is local (AV:L), requires low privileges (PR:L), and depends on user interaction — specifically, convincing a target to open the malicious file. No public proof-of-concept or technical write-up has been identified at this time (NVD, NVIDIA Advisory).

Successful exploitation can result in code execution, denial of service, information disclosure, and data tampering on the affected system. The attacker gains the same privilege level as the user running the NeMo Framework application, meaning confidentiality, integrity, and availability are all fully compromised (rated High for each). While the scope is unchanged (no container/sandbox escape implied), the compromise of an AI/ML development environment could expose sensitive model weights, training data, and research assets, and may serve as a foothold for lateral movement within a data science or MLOps pipeline (NVD, Feedly).

As of the time of reporting, there is no public proof-of-concept exploit and no evidence of in-the-wild exploitation (Feedly). No threat actor attribution has been identified. The EPSS score is approximately 0.172%, indicating a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires social engineering to convince a user to load a malicious file, which somewhat limits opportunistic exploitation (NVD).

1. Craft malicious file: Create a serialized Python object (e.g., using pickle or a similar serialization format supported by NeMo) that embeds a malicious payload — such as a reverse shell command — within the deserialized object's __reduce__ or equivalent method.
2. Social engineering: Deliver the malicious file to a target user who has NVIDIA NeMo Framework (version < 2.6.1) installed, disguising it as a legitimate NeMo model checkpoint, configuration, or dataset file (e.g., .nemo or .pkl file).
3. Trigger deserialization: Convince the target to load the file using NeMo's standard file-loading APIs or CLI commands (e.g., nemo.core.classes.modelPT.ModelPT.restore_from() or similar restore/load functions).
4. Achieve code execution: Upon deserialization, the embedded payload executes with the privileges of the user running NeMo, enabling actions such as spawning a reverse shell, exfiltrating model data, or establishing persistence on the host system (NVD, NVIDIA Advisory).

• Process: Unexpected child processes spawned by the Python interpreter running NeMo (e.g., bash, sh, curl, wget, nc) during or immediately after a file load operation.
• Network: Outbound connections from the NeMo host to unknown external IP addresses or domains shortly after loading a NeMo model or configuration file, particularly on non-standard ports.
• File System: Unexpected new files written to the NeMo working directory, /tmp, or user home directories (e.g., scripts, binaries, or cron job entries) following a file load event.
• Logs: Python tracebacks or unusual exceptions in application logs related to deserialization or object loading; OS-level audit logs (e.g., auditd) showing unexpected execve calls from the NeMo Python process.

NVIDIA has released a fix in NeMo Framework version 2.6.1; all users should upgrade immediately (NVIDIA Advisory). As interim workarounds, restrict NeMo file loading to trusted, verified sources only, and implement access controls limiting which users can load NeMo framework files. Consider running NeMo processes in sandboxed or containerized environments to limit the blast radius of any successful exploitation. Monitor for suspicious file loading activity in environments running NeMo prior to patching.

The vulnerability received brief coverage on social media platforms including Mastodon, with security aggregators such as CVEFeed and VulnDB tracking the disclosure. Red Hat published a security advisory entry for the CVE, and GitLab's advisory database also catalogued the issue for the nemo-toolkit PyPI package (GitLab Advisory, Red Hat). No significant independent researcher commentary or major media coverage has been identified beyond standard vulnerability tracking.