> CVE-2026-81722 [HIGH]

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PUBLISHED
2026-08-27 17:21
MODIFIED
2026-08-27 17:21
CVSS_SCORE V3
8.7
EPSS (Prob. Exploit)
0.52%
Top 56.6%
DATA SOURCES:
NVD đź”— 2026-08-27 CWE MITRE đź”— 2026-09-01 FIRST EPSS đź”— 2026-10-25 GITHUB đź”— 2026-10-29 OSV đź”— 2026-09-02

> 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_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

> MÉTRIQUES CVSS DÉTAILLÉES

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Network (N)
Exploit possible à distance via réseau (HTTP, API, etc.)
AC (Complexité d'Attaque)
Attack Complexity
Low (L)
Peu de conditions requises pour exploiter
PR (Privilèges Requis)
Privileges Required
None (N)
Aucune authentification requise
UI (Interaction Utilisateur)
User Interaction
None (N)
Aucune interaction utilisateur nécessaire
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
None (N)
Aucune divulgation d'informations
I (Impact Intégrité)
Integrity Impact
None (N)
Aucune modification de données possible
A (Impact Disponibilité)
Availability Impact
High (H)
Interruption totale du service possible

> RÉSUMÉ DES IMPACTS

Confidentialité
None
Aucune divulgation d'informations
Intégrité
None
Aucune modification de données possible
Disponibilité
High
Interruption totale du service possible

> WEAKNESSES

CWE-407

> CWE DETAILED DESCRIPTIONS

CWE-407: Inefficient Algorithmic Complexity - An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

> RED HAT SECURITY ADVISORIES

Red Hat Security Advisory: RHOAI 3.5.1 - Red Hat OpenShift AI
Updated images are now available for Red Hat OpenShift AI.
Red Hat Security Advisory: RHOAI 3.3.7 - Red Hat OpenShift AI
Updated images are now available for Red Hat OpenShift AI.
Red Hat Security Advisory: RHOAI 3.4.5 - Red Hat OpenShift AI
Updated images are now available for Red Hat OpenShift AI.
Red Hat Security Advisory: RHOAI 2.25.12 - Red Hat OpenShift AI
Updated images are now available for Red Hat OpenShift AI.
Red Hat Security Advisory: RHOAI 3.5.2 - Red Hat OpenShift AI
Updated images are now available for Red Hat OpenShift AI.

> GITHUB SECURITY ADVISORY

GHSA-ww6m-cw3f-q94g MODERATE

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

AFFECTED PACKAGES:
PIP / nltk
<= 3.10.2
Fixed in: 3.10.3

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

nltk PorterStemmer before 3.10.3 Quadratic-time DoS

AFFECTED PACKAGES:
Unknown / Unknown
49 versions affected
ALIASES:
GHSA-ww6m-cw3f-q94g, PYSEC-2026-3738

> HISTORIQUE DES MODIFICATIONS

Première apparition
27/08/2026 17:21
Source: NVD
📊 ENRICHISSEMENT 01/09/2026 06:02
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-407: Inefficient Algorithmic Complexity - An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an ...
Total des modifications: 1 Dernière mise à jour: 1 month ago

> REFERENCES

https://github.com/nltk/nltk/security/advisories/GHSA-ww6m-cw3f-q94g
https://www.vulncheck.com/advisories/nltk-porterstemmer-before-3.10.3-quadratic-...
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