---
cve: "CVE-2026-66046"
severity: "HIGH"
cvss: 8.7
epss: "68%"
vendor: "libexpat project"
kev: false
exploited: false
published: "2026-08-18 15:16:57"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-07T19:28:22+02:00"
---

# CVE-2026-66046

> 8.7 HIGH · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- 92810461043fce37e70079b37ab1f04490a8f039 (Commit)

## Referenzen

- <https://github.com/libexpat/libexpat/pull/1321>
- <https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-66046) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_