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

CVE ID :CVE-2026-81722
Published : Aug. 27, 2026, 5:21 p.m. | 1 hour, 8 minutes ago
Description :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.
Severity: 8.7 | HIGH
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