Low severity3.7NVD Advisory· Published Aug 27, 2026· Updated Sep 1, 2026
CVE-2026-81725
CVE-2026-81725
Description
NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.
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
2Patches
Vulnerability mechanics
References
7- github.com/nltk/nltk/security/advisories/GHSA-8mpw-7fpc-4gqjnvdExploitVendor AdvisoryWEB
- github.com/advisories/GHSA-8mpw-7fpc-4gqjghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-81725ghsaADVISORY
- www.vulncheck.com/advisories/nltk-before-3.10.3-regular-expression-denial-of-service-via-pl196xcorpusreadernvdThird Party AdvisoryWEB
- github.com/nltk/nltk/commit/7808692d451b962711005d954859bb83aabcf8faghsaWEB
- github.com/nltk/nltk/releases/tag/v3.10.3ghsaWEB
- github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3752.yamlghsaWEB
News mentions
1- Nltk Library: 16 Vulnerabilities Including Critical RCE Disclosed in BatchVypr Intelligence · Aug 27, 2026