CVE intelligence

CVE-2026-66046

Vulnerability intelligence

Published Aug 18, 2026Sources checked Oct 28, 2026

7.5HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-66046 and is rated High severity with a CVSS score of 7.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Sep 5, 2026

See the Microsoft Security Update Guide for the update that applies to your product.

Vendor-listed releases

2.8.3-2

CISA KEVNot listedBased on the latest collected catalog

EPSS0.7%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-66046?

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.

Source: NVD