VDB
CVE-2026-81724
CVE-2026-81724
PUBLISHED
CVSS 6.9 MEDIUM
Reported by VulnCheck · Published August 27, 2026
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.
Risk Scores
CVSS 4.0
6.9
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
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| nltk | nltk | 0, 3.10.3 |
| nltk | nltk | 0, 3.10.3 |
| wolfi | open-webui | 0 |
| chainguard | open-webui | 0 |
| chainguard | nemo | 0 |
| PyPI | nltk | 0 |
Timeline
- Aug 27, 2026 Coalition ESS Score
- Aug 27, 2026 CVE Published
- Aug 28, 2026 EPSS Score
- Sep 1, 2026 EPSS Score
- Sep 2, 2026 Security Advisory
- Sep 6, 2026 EPSS Score
- Sep 9, 2026 EPSS Score
- Sep 12, 2026 EPSS Score
- Sep 16, 2026 EPSS Score
- Sep 18, 2026 EPSS Score
- Sep 24, 2026 EPSS Score
- Sep 26, 2026 EPSS Score
References
- GitHub Security Advisory (GHSA-cw6x-m8jw-qmrh) vendor-advisory
- VulnCheck Advisory: NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion third-party-advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-81724 advisory
- https://github.com/advisories/GHSA-cw6x-m8jw-qmrh advisory
- https://github.com/nltk/nltk/commit/43c7b78cc8ea37e5cd3a129e27e32c415ea21cf1 patch
- https://github.com/nltk/nltk/releases/tag/v3.10.3 url
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3739.yaml advisory