GHSA-ww6m-cw3f-q94g: nltk (CVE-2026-81722)

Package	Ecosystem	Affected	Fixed in
nltk	PyPI	<3.10.3	3.10.3

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

NLTK versions before 3.10.3 are affected. Calling the PorterStemmer stem() function on a very long token made of repeated 'y' characters, followed by a suffix such as 'ness', takes quadratic time, so a single token of roughly 20 to 50 KB can tie up a CPU core. An attacker who can supply text to be stemmed can cause denial of service; the advisory reports no confidentiality or integrity impact. Upgrade to NLTK 3.10.3 or later.

Written 4 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
8.7	High	4.0	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N	CNA (VulnCheck)

CISA KEV Not listed.
EPSS 0.0052, the 44th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:29 UTC First seen by agentprime
31 Oct 2026, 14:29 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.