Is CVE-2026-81722 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-81722?

CVE-2026-81722 has a CVSS v3 severity of HIGH (7.5).

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CVE-2026-81722

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.