> CVE-2026-66046 [HIGH]

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PUBLISHED
2026-08-18 15:16
MODIFIED
2026-08-18 15:16
CVSS_SCORE V3
8.7
EPSS (Prob. Exploit)
0.74%
Top 46.2%
DATA SOURCES:
NVD đź”— 2026-08-18 CWE MITRE đź”— 2026-09-01 FIRST EPSS đź”— 2026-10-18 OSV đź”— 2026-10-26 MSRC đź”— 2026-09-01

> DESCRIPTION

Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.

> 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: expat security update
An update for expat is now available for Red Hat Enterprise Linux 8. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CV...
Red Hat Security Advisory: expat security update
An update for expat is now available for Red Hat Enterprise Linux 9. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CV...
Red Hat Security Advisory: expat security update
An update for expat is now available for Red Hat Enterprise Linux 10. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (C...
Red Hat Security Advisory: Red Hat Cost Management On-Premise container image update
Updated container image for Red Hat Cost Management On-Premise is now available.
Red Hat Security Advisory: Red Hat Update Infrastructure 5.3 security update
The latest release of Red Hat Update Infrastructure. For more details, see the product documentation.

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

Expat Denial of Service via storeAtts() Quadratic Complexity

AFFECTED PACKAGES:
Unknown / Unknown
70 versions affected

> HISTORIQUE DES MODIFICATIONS

Première apparition
18/08/2026 15:16
Source: NVD
đź“Š 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/libexpat/libexpat/pull/1321
https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadr...
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