NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
Published Aug 22, 2026 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- MEDIUM
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
- Patch commit ↗
- Source repository ↗
- Source repository ↗
- VulnCheck Advisory: NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass ↗
Record history
Published Aug 22, 2026 · Last refreshed Nov 3, 2026