Fluid Attacks Database

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.

Mitigation

Update Impact

Minimal update. May introduce new vulnerabilities or breaking changes.

Ecosystem	Component	Affected version	Patched versions
debian 11	nltk	=3.10.0-1 \|\| =3.10.1-1 \|\| =3.10.3-1 \|\| =3.5-1 \|\| =3.6.5-1 \|\| =3.6.7-1 \|\| =3.7-1 \|\| =3.8-1 \|\| =3.8.1-1 \|\| =3.9.1-1 \|\| =3.9.1-2 \|\| =3.9.2-1 \|\| =3.9.3-1	-
debian 12	nltk	=3.10.0-1 \|\| =3.10.1-1 \|\| =3.10.3-1 \|\| =3.8-1 \|\| =3.8.1-1 \|\| =3.9.1-1 \|\| =3.9.1-2 \|\| =3.9.2-1 \|\| =3.9.3-1	-
debian 13	nltk	=3.10.0-1 \|\| =3.10.1-1 \|\| =3.10.3-1 \|\| =3.9.1-2 \|\| =3.9.2-1 \|\| =3.9.3-1	-
debian 14	nltk	=3.10.0-1 \|\| =3.10.1-1 \|\| =3.9.1-2 \|\| =3.9.2-1 \|\| =3.9.3-1 \|\| >=0 <3.10.3-1	3.10.3-1

Aliases

1. CVE-2026-817222. NVD-2026-817223. OSV-DEBIAN-2026-817224. OSV-2026-817225. SECURITY-TRACKER-CVE-2026-81722

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