CVE-2026-81722nltk PorterStemmer before 3.10.3 Quadratic-time DoS
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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nltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). The _is_consonant() helper walks backward over the entire run of trailing 'y' characters on every call, and _measure() invokes it for each stem position, causing O(n^2) behavior. A single ~20-50 KB untrusted token consisting of a long run of the letter 'y' followed by a matching suffix (e.g., 'ness') can pin a CPU core for seconds to minutes, causing availability impact.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-407
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulnCheck
- NVD analysis
- Analyzed
- Record last updated
- Aug 27, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
References
- https://github.com/nltk/nltk/security/advisories/GHSA-ww6m-cw3f-q94gvendor-advisory, exploit
- https://www.vulncheck.com/advisories/nltk-porterstemmer-before-3.10.3-quadratic-time-dosthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.