---
cve: "CVE-2026-93990"
severity: "HIGH"
cvss: 8.7
epss: "0.4%"
vendor: "libexpat"
kev: false
exploited: false
published: "2026-09-19 23:17:10"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-24T11:22:08+02:00"
---

# CVE-2026-93990

> 8.7 HIGH · 🧪 PoC

## Beschreibung

Expat through 2.8.4 fails to validate low surrogates following high surrogates in UTF-16 input, allowing malformed UTF-16 sequences to be accepted. Attackers can craft UTF-16 encoded XML with lone high surrogates that consume following code units, hiding markup characters from the parser and enabling XML injection attacks.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/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)

- 12cf0b1f25f026a022fe728ad8f7e3d017285b80 (Commit)
- ff6e1d7e750bbe245178f51a47a965dc8342861a (Commit)

## Referenzen

- <https://github.com/libexpat/libexpat/pull/1282>
- <https://github.com/libexpat/libexpat/commit/ff6e1d7e750bbe245178f51a47a965dc8342861a>
- <https://github.com/libexpat/libexpat>
- <https://www.vulncheck.com/advisories/expat-through-2.8.4-malformed-utf-16-acceptance-via-unchecked-surrogate>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-93990) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_