by Kastro
Paper/Archive/CVE-2026-78683

CVE-2026-78683

nltk nltk — NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization

EPSS 0.5%public exploitCVSS 9.6
critical.is priorityof 100
48
CVSS 9.6 (CNA)9.6 / 10 × 3028.8Not in CISA KEV+300.0EPSS percentile 43.6.436 × 208.7Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
nltk< 3.10.03.10.0CNA

Scores by source

VulnCheck (CNA)9.6CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
VulnCheck (CNA)9.4CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CISA ADPSSVCExploitation: poc · Automatable: no · Technical impact: total

References

exploitgithub.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2writeupvulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization