NLTK up to 3.10.2 PorterStemmer PorterStemmer.stem denial of service

CVSS Meta Temp Score
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CTI Interest Score
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6.3$0-$5k0.00+

Summaryinfo

A vulnerability labeled as problematic has been found in NLTK up to 3.10.2. Impacted is the function PorterStemmer.stem of the component PorterStemmer. Executing a manipulation can lead to denial of service. This vulnerability is registered as CVE-2026-81722. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability classified as problematic was found in NLTK up to 3.10.2. This vulnerability affects the function PorterStemmer.stem of the component PorterStemmer. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-81722 since 08/27/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 3.10.3 eliminates this vulnerability.

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Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 6.4
VulDB Meta Temp Score: 6.3

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.5
CNA Vector (VulnCheck): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Denial of service
CWE: CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: NLTK 3.10.3

Timelineinfo

08/27/2026 Advisory disclosed
08/27/2026 +0 days CVE reserved
08/27/2026 +0 days VulDB entry created
08/27/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-81722 (🔒)
GCVE (CVE): GCVE-0-2026-81722
GCVE (VulDB): GCVE-100-396280

Entryinfo

Created: 08/27/2026 20:10
Changes: 08/27/2026 20:10 (76)
Complete: 🔍
Cache ID: 216::103

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