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
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 wi
Affected packages
No package-level mapping for this advisory.
Exploit signal
- Known exploited (CISA KEV)
- No
- EPSS score
- —
- EPSS percentile
- —
EPSS is the probability a CVE is exploited in the wild; percentile is its rank among all CVEs.
Sources
- https://www.cve.org/CVERecord?id=CVE-2026-78683
- https://github.com/cveproject/cvelistv5/tree/main/cves/2026/78xxx/cve-2026-78683.json
- https://github.com/nltk/nltk/security/advisories/ghsa-rhp5-r9x4-f5g2
- https://nvd.nist.gov/vuln/detail/cve-2026-78683
- https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization
Structured record: https://ubuntu.com/security/CVE-2026-78683
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