Deserialization in Nltk
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.
Vulnerability class: Insecure Deserialization
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.011 (64.4th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 64th percentile — 64.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.011 · change: +0.003
Affected products
Weakness classification (CWE)
References
- github.com/nltk/nltk/commit/c3e37113742a1ebeeb4f2ca58941f320f98805ea (Patch, patch)
- github.com/nltk/nltk (Product, product)
- github.com/nltk/nltk/blob/v3.10.2/nltk/picklesec.py (Product, technical-description)
- www.vulncheck.com/advisories/nltk-through-remote-code-execution-via-allowlistun… (Patch, Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-71513?
- CVE-2026-71513 is a high-severity vulnerability in Nltk, classified under Deserialization of Untrusted Data. CVSS score: 8.8/10. Published 2026-08-22.
- How severe is CVE-2026-71513?
- High severity. CVSS v3 base score is 8.8 out of 10.