VULNERABILITY INTELLIGENCE

CVE-2026-81722

CVSS score7.5 HIGH
EPSS probability0.52%
CISA KEVNot currently listed
Published2026-08-27
Last modified2026-08-31
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Weakness classification

  • disclosure@vulncheck.com: CWE-407

Primary references