---
cve: "CVE-2026-84129"
severity: "CRITICAL"
cvss: 9.8
epss: "0.3%"
vendor: "Generic Security"
kev: false
exploited: false
published: "2026-09-01 12:18:56"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-10-25T16:01:47+01:00"
---

# CVE-2026-84129

> 9.8 CRITICAL

## Beschreibung

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

## CNA-Record (Kanon, cvelistV5)

- CNA: **mozilla**
- State: PUBLISHED
- Stand: 2026-09-02 15:49:17

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **yes**
  - Technical Impact: **total**

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Schwachstellen-Klasse

- **CWE-346** — Origin Validation Error
  The product does not properly verify that the source of data or communication is valid.

## Angriffsmuster (CAPEC)

- [CAPEC-21 — Exploitation of Trusted Identifiers](https://capec.mitre.org/data/definitions/21.html) _(Severity: High)_
- [CAPEC-111 — JSON Hijacking (aka JavaScript Hijacking)](https://capec.mitre.org/data/definitions/111.html) _(Severity: High)_
- [CAPEC-141 — Cache Poisoning](https://capec.mitre.org/data/definitions/141.html) _(Severity: High)_
- [CAPEC-142 — DNS Cache Poisoning](https://capec.mitre.org/data/definitions/142.html) _(Severity: High)_
- [CAPEC-160 — Exploit Script-Based APIs](https://capec.mitre.org/data/definitions/160.html) _(Severity: Medium)_
- [CAPEC-384 — Application API Message Manipulation via Man-in-the-Middle](https://capec.mitre.org/data/definitions/384.html) _(Severity: Low)_
- [CAPEC-385 — Transaction or Event Tampering via Application API Manipulation](https://capec.mitre.org/data/definitions/385.html) _(Severity: Medium)_
- [CAPEC-386 — Application API Navigation Remapping](https://capec.mitre.org/data/definitions/386.html) _(Severity: Medium)_

## ATT&CK-Techniken

- [T1134 — Access Token Manipulation](https://attack.mitre.org/techniques/T1134/)
- [T1528 — Steal Application Access Token](https://attack.mitre.org/techniques/T1528/)
- [T1539 — Steal Web Session Cookie](https://attack.mitre.org/techniques/T1539/)
- [T1557.002 — Adversary-in-the-Middle: ARP Cache Poisoning](https://attack.mitre.org/techniques/T1557/002/)
- [T1584.002 — Compromise Infrastructure: DNS Server](https://attack.mitre.org/techniques/T1584/002/)

## BSI-Hinweise (deutsch)

- [Mozilla Firefox und Thunderbird: Mehrere Schwachstellen](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-3132) — _BSI-Einstufung: hoch_
  Ein Angreifer kann mehrere Schwachstellen in Mozilla Firefox und Thunderbird ausnutzen, um Berechtigungen zu erweitern, Sicherheitsmaßnahmen zu umgehen, sensible Informationen offenzulegen, Daten zu manipulieren, Spoofing-Angriffe durchzuführen, möglicherweise durch Speicherbeschädigungen beliebigen Code auszuführen oder Denial-of-Service-Zustände herbeizuführen.

## Referenzen

- <https://bugzilla.mozilla.org/show_bug.cgi?id=2055028>
- <https://www.mozilla.org/security/advisories/mfsa2026-82/>
- <https://www.mozilla.org/security/advisories/mfsa2026-85/>
- <https://www.mozilla.org/security/advisories/mfsa2026-86/>
- <https://www.mozilla.org/security/advisories/mfsa2026-88/>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-84129/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_