---
cve: "CVE-2026-118370"
severity: "HIGH"
cvss: 8.2
epss: "0.4%"
vendor: "libexpat"
kev: false
exploited: false
published: "2026-10-28 03:17:13"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-11-08T16:35:55+01:00"
---

# CVE-2026-118370

> 8.2 HIGH · 🧪 PoC

## Beschreibung

libexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory.

## CNA-Record (Kanon, cvelistV5)

- CNA: **VulnCheck**
- State: PUBLISHED
- Stand: 2026-11-02 19:56:23
- CNA-CVSS: **8.2** (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **no**
  - Technical Impact: **partial**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:H/AT:P/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 | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Schwachstellen-Klasse

- **CWE-190** — Integer Overflow or Wraparound
  The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

## Angriffsmuster (CAPEC)

- [CAPEC-92 — Forced Integer Overflow](https://capec.mitre.org/data/definitions/92.html) _(Severity: High)_

## Patch verfügbar (OSV)

- 1bac53c4fc460a03cd9860f39501c7979f6750ae (Commit)
- 621cb2c78b253ee023a86bc91d6ddb048481c04c (Commit)

## BSI-Hinweise (deutsch)

- [expat: Mehrere Schwachstellen ermöglichen Denial of Service](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-4214) — _BSI-Einstufung: mittel_
  Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in expat ausnutzen, um einen Denial of Service Angriff durchzuführen.

## Referenzen

- <https://github.com/libexpat/libexpat/pull/1450>
- <https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750ae>
- <https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04c>
- <https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140>
- <https://github.com/libexpat/libexpat>
- <https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixes>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-118370/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_