medium6.3
CVE-2026-81725
NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption…
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | nltk | <= 3.10.2 | 3.10.3 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Nltk | Nltk | before 3.10.3 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-8mpw-7fpc-4gqj
- https://github.com/nltk/nltk/security/advisories/GHSA-8mpw-7fpc-4gqj
- https://nvd.nist.gov/vuln/detail/CVE-2026-81725
- https://github.com/nltk/nltk/commit/7808692d451b962711005d954859bb83aabcf8fa
- https://github.com/nltk/nltk/releases/tag/v3.10.3
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3752.yaml
- https://www.vulncheck.com/advisories/nltk-before-3.10.3-regular-expression-denial-of-service-via-pl196xcorpusreader