CVE-2026-71513

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

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

8.8CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

1.1% chance of exploitation in the next 30 days; higher than 65% of CVEs (scores of 2026-10-25)

CWE

CWE-502

Published

2026-08-22

Modified

2026-10-14

Record from

the NVD, synced 2026-10-19

Affected

• nltk:nltk

Packages (OSV)

References

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

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