GHSA-8x48-8g7j-rqxp

Duplicate Advisory: Quadratic-time DoS in PorterStemmer via long runs of 'y'

Published

2026-08-27

Modified

2026-09-02

Sources

github-advisory

Summary

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-ww6m-cw3f-q94g. This link is maintained to preserve external references. ## Original 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.

Affected packages

Remediation: No patched version is listed by GitHub.

References

• https://github.com/advisories/GHSA-8x48-8g7j-rqxp