Medium severity5.3NVD Advisory· Published Aug 27, 2026· Updated Aug 31, 2026
CVE-2026-81724
CVE-2026-81724
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
nltkPyPI | < 3.10.3 | 3.10.3 |
Affected products
5- osv-coords3 versions
< 2.7.3-r27+ 2 more
- (no CPE)range: < 2.7.3-r27
- (no CPE)range: < 0.11.3-r1
- (no CPE)range: < 0.11.3-r1
Patches
Vulnerability mechanics
References
7- github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrhnvdExploitVendor AdvisoryWEB
- github.com/advisories/GHSA-cw6x-m8jw-qmrhghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-81724ghsaADVISORY
- www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursionnvdThird Party AdvisoryWEB
- github.com/nltk/nltk/commit/43c7b78cc8ea37e5cd3a129e27e32c415ea21cf1ghsaWEB
- github.com/nltk/nltk/releases/tag/v3.10.3ghsaWEB
- github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3739.yamlghsaWEB
News mentions
1- Nltk Library: 16 Vulnerabilities Including Critical RCE Disclosed in BatchVypr Intelligence · Aug 27, 2026