EUVD-2026-65229
GHSA-gx65-c5hj-vpv5
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Malicious model may be delivered over the network (AV:N) but a user/app must load it (UI:R); pickle RCE runs as the loading user with no privilege boundary crossed, so S:U and full C/I/A:H.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionCVE.org
NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.
Articles & Coverage 1
AnalysisAI
Arbitrary code execution in NLTK (Natural Language Toolkit) through 3.9.4 allows attackers to run Python code when a victim application loads a malicious transition-parser model file. The TransitionParser.parse() method deserializes model data via pickle with restricted=False, so an attacker-supplied model embedding pickle gadget chains executes with the privileges of the loading process. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires that the victim application load an attacker-crafted TransitionParser model file through the TransitionParser.parse() code path - the CVSS UI:P element reflects that exploitation is not fully autonomous and hinges on a model-loading action. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:P, base 9.4) rates this critical, and the impact is genuine full code execution (VC/VI/VA:H). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker publishes or substitutes a malicious NLTK transition-parser model file - for example in a public model repository, a shared internal artifact store, or as a user-uploaded 'trained model'. A data pipeline or application calls TransitionParser.parse() and loads the file, causing the embedded pickle gadget chain to execute arbitrary Python code as the pipeline's service account. … |
| Remediation | Vendor-released patch: upgrade to NLTK 3.10.0 or later, which fixes the unsafe deserialization path (advisory GHSA-rhp5-r9x4-f5g2). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all systems running NLTK versions up to 3.9.4 and identify which applications load external or user-supplied model files, prioritizing production systems handling sensitive data. …
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
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External POC / Exploit Code
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