CVE-2026-81722nltk PorterStemmer before 3.10.3 Quadratic-time DoS

Descripción

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.

Datos: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Se publican tal como los indican las fuentes, en inglés.

Productos y versiones afectados

Referencias y parches

• GitHub Security Advisory (GHSA-ww6m-cw3f-q94g) vendor-advisoryExploitVendor Advisory
• VulnCheck Advisory: nltk PorterStemmer before 3.10.3 Quadratic-time DoS third-party-advisoryThird Party Advisory