NLTK · GHSA-rg32-vgf9-927c · Package
NO FIX YET · SEE WHAT TO DO
NLTK's TreebankWordTokenizer.span_tokenize uses repeated list.pop(0) calls, so long runs of double-quote characters make CPU use grow quadratically. An attacker who can submit text to a service that span-tokenizes it can exhaust a CPU core and degrade availability.
first public Nov 13, 2026 · 1 source
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Services that run NLTK's Treebank word tokenizer on text submitted by outside users are exposed, because a single long quote run can tie up a CPU core. Applications that tokenize only trusted or internal text can skip it. The advisory is withdrawn as a duplicate, so the canonical record is GHSA-ffr9-mgrr-wcvr.
Not affected if no-untrusted-tokenization, trusted-input-only
Who cares nlp, nltk, python
pip show nltkspan_tokenize on untrusted inputnltk to 3.10.4 or later (this advisory is withdrawn as a duplicate of GHSA-ffr9-mgrr-wcvr, which the sources do not detail)This advisory has been withdrawn because it is a duplicate of GHSA-ffr9-mgrr-wcvr. This link is maintained to preserve external references.
NLTK from 3.2.5 before 3.10.4 contains an algorithmic complexity vulnerability in TreebankWordTokenizer.span_tokenize that allows remote attackers to cause quadratic CPU consumption through repeated list.pop(0) calls. Attackers can submit long runs of double-quote characters to services span-tokenizing untrusted text, exhausting a CPU core and degrading availability.
This page as .md · .json · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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