Mozilla Firefox and Thunderbird: Privilege escalation in DOM Navigation component
Summary
A privilege escalation flaw in the DOM Navigation component of Mozilla Firefox and Thunderbird is fixed in Firefox 159 and Thunderbird 159. Mozilla rates the CVSS 3.1 base score at 8.8 (High), with network access, no privileges and user interaction required, and high impact on confidentiality, integrity and availability. In practice, a user would need to visit a malicious or compromised page or open a link. The CNA record reports no known exploitation and CISA SSVC rates automatable as no.
Affected
- Mozilla Firefox (versions before 159 per the vendor advisory; exact range unconfirmed in the CVE record)
- Mozilla Thunderbird (versions before 159; exact range unconfirmed)
- Ubuntu 22.04 LTS: Thunderbird listed as vulnerable, no fixed package version given
Fixed in
- Firefox 159
- Thunderbird 159
Workaround
Unknown.
Exploitation
- No known exploitation in the wild as of 27 Oct 2026 (OffSeq, no CISA KEV listing)
- No public proof of concept found as of 26 Oct 2026
- CISA SSVC: exploitation none, automatable no, technical impact total
- EPSS: 0.35 %
Our recommendation
- Update Firefox and Thunderbird to version 159 or later through the normal update cycle
- Check the ESR advisories MFSA 2026-119 and MFSA 2026-120 and update ESR installations accordingly
- Inventory browser and mail clients and prioritise browser fleets, as they are internet-facing
- Monitor the Mozilla advisories for updates to version details and exploitation status
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Mozilla MFSA 2026-118 (Firefox 159) www.mozilla.org
- Mozilla MFSA 2026-121 (Thunderbird 159) www.mozilla.org
- Mozilla Bugzilla 2075440 bugzilla.mozilla.org
- Ubuntu CVE tracker ubuntu.com
- OffSeq threat radar radar.offseq.com
- VulDB vuldb.com
- Strix CVE-2026-118008 www.strix.ai
- Tenable Thunderbird plugin www.tenable.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 10:14.
Original description (NVD)
Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 159 and Thunderbird 159.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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