CVE-2026-79657
NLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead of specific safe callables.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.21%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
NLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead of specific safe callables. Attackers can craft malicious pickle payloads invoking dangerous in-namespace functions like ReppTokenizer._execute and numpy.f2py.crackfortran.myeval through pickle REDUCE to execute arbitrary commands during model or tokenizer artifact loading.
- CVSS 4.0
- 9.3 CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/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/M
- EPSS
- 1.21% probability · 67th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-502
- Affected
- nltk/nltk
- Source
- disclosure@vulncheck.com
References
- https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfwExploit, Vendor Advisory
- https://www.vulncheck.com/advisories/nltk-before-3.10.3-remote-code-execution-via-unsafe-pickle-deserializationThird Party Advisory
- https://github.com/nltk/nltk/security/advisories/GHSA-x99w-6fgc-pmfwExploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.