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AI security incident: Fickling has safety check bypass via REDUCE+BUILD opcode sequence (GHSA-mhc9-48gj-9gp3)

Incident date: February 25, 2026 | Published: February 25, 2026 | Source: GitHub Security Advisory | Classification confidence: 64%

This incident is part of the public archive and includes explicit AI-related signals from the cited source material. Review methodology.

Assessment It is believed that the analysis pass works as intended, REDUCE and BUILD are not at fault here. The few potentially unsafe modules have been added to the blocklist (https://github.com/trailofbits/fickling/commit/0c4558d950daf70e134090573450ddcedaf10400). # Original report ### Summary All 5 of fickling's safety interfaces — is_likely_safe() , check_safety() , CLI --check-safety , always_check_safety() , and the check_safety() context manager — report LIKELY_SAFE / raise no exceptions for pickle files that call dangerous top-level stdlib functions (signal handlers, network servers, network connections, file operations) when the REDUCE opcode is followed by a BUILD opcode.

Why This Is AI-Related

This page is treated as AI-specific because the source material references fickling, which places the issue inside an AI workflow, model, assistant, or supporting dependency rather than a generic software bulletin.

  • fickling

Affected Workflow

Model registries, artifact scanners, notebook workflows, and CI/CD steps that handle model files need immediate review.

Likely Attack Path

The malicious payload is embedded in model artifacts or serialized objects, then executes or bypasses scanning during load and inspection.

Impact

The advisory affects model artifacts or serialized AI assets, which can bypass inspection or execute during load and validation steps. Severity HIGH. Classification confidence 64%. Source channel GHSA.

Detection And Triage Signals

  • New or unsigned model artifacts entering the registry
  • Scanner output gaps for pickle or custom model formats
  • Unexpected code paths during model loading or validation jobs

Recommended Response

  • Inventory model artifacts, serialized objects, and scanners that touch the affected package or workflow.
  • Block untrusted model files and revalidate registry, CI, or notebook loading paths before restoring normal operation.
  • Review artifact provenance, scanner output, and recent model-ingestion activity for suspicious changes.

Compliance And Business Impact

Model artifact compromise undermines trust in the training and deployment chain and can create stealthy persistence in ML workflows.

Sources

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