CVE-2026-81724
NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion
- State
- Published
- Severity
- 6.9 Medium
- Published
- Aug 27, 2026
- Updated
- Aug 27, 2026
- Reserved
- Aug 27, 2026
Description
NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.9 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | VulnCheck |
Weaknesses
- CWE-674 Uncontrolled Recursion
Affected Products
| Product | Versions |
|---|---|
nltknltk |
|
References
- GitHub Security Advisory (GHSA-cw6x-m8jw-qmrh)vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 Denial of Service via Uncontrolled Recursionthird-party-advisory
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