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Vulnerability record · CVE-2026-71513 · published 22 August 2026

CVE-2026-71513: Nltk deserialization of untrusted data vulnerability

Nltk · Nltk

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.

8.7 CVSS 4.0 High EPSS 1.1% · top 35.8% CWE-502 · Deserialization of untrusted data
8.7CVSS 4.0 base score
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
16 Sep 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/nltk/nltk Product
https://github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py#L119-L124 Product
https://github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea Patch
https://www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistunpickler-dotted-name-bypass Third Party AdvisoryPatch

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-71513), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.