Resource exhaustion in Nltk
CVE-2026-81723
NLTK versions before 3.10.3 contain a quadratic CPU exhaustion vulnerability in XMLCorpusView._read_xml_fragment() that rescans accumulated XML fragments on every 1 KiB block read. Attackers can provide malformed XML corpus files to cause severe CPU consumption and denial of service through affected readers like BNCCorpusReader.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.003 (18.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 18.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/nltk/nltk/security/advisories/GHSA-vp2x-qp44-57v7 (vendor-advisory)
- www.vulncheck.com/advisories/nltk-before-3.10.3-quadratic-cpu-exhaustion-via-xm… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-81723?
- CVE-2026-81723 is a low-severity vulnerability in Nltk, classified under Uncontrolled Resource Consumption. CVSS score: 3.7/10. Published 2026-08-27.
- How severe is CVE-2026-81723?
- Low severity. CVSS v3 base score is 3.7 out of 10.