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.
Metrics
Affected Vendors & Products
References
History
Tue, 01 Sep 2026 12:15:00 +0000
| Type | Values Removed | Values Added |
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| Weaknesses | CWE-606 | |
| References |
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| Metrics |
threat_severity
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threat_severity
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Thu, 27 Aug 2026 18:00:00 +0000
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ssvc
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Thu, 27 Aug 2026 16:45:00 +0000
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| 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. | |
| Title | nltk PorterStemmer before 3.10.3 Quadratic-time DoS | |
| First Time appeared |
Nltk
Nltk nltk |
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| Weaknesses | CWE-407 | |
| CPEs | cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Nltk
Nltk nltk |
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| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: VulnCheck
Published: 2026-08-27T14:51:15.857Z
Updated: 2026-08-27T17:49:54.623Z
Reserved: 2026-08-27T11:13:14.064Z
Link: CVE-2026-81722
Updated: 2026-08-27T17:49:23.759Z
Status : Analyzed
Published: 2026-08-27T17:21:02.800
Modified: 2026-08-31T15:44:19.437
Link: CVE-2026-81722