Mozilla Firefox/Thunderbird: Incorrect boundary conditions in SVG component
Summary
Mozilla Firefox and Thunderbird contain a memory-handling flaw (incorrect boundary conditions) in the SVG component. Mozilla rates the impact as high and reports no details beyond the advisory text. An attacker could potentially exploit it by getting a user to open crafted SVG content or visit a malicious page; this is an inference, as Mozilla does not describe the attack path. The CVSS score is disputed across sources.
Affected
- Mozilla Firefox before 158.0.1
- Mozilla Thunderbird before 158.0.1
- Firefox ESR: Unknown (not verified; check MFSA 2026-112 and 2026-113)
Fixed in
- Mozilla Firefox 158.0.1
- Mozilla Thunderbird 158.0.1
- Later releases exist; use the latest version
Workaround
Unknown. No workaround is documented; apply the vendor update.
Exploitation
- No known in-the-wild exploitation found
- Not listed in CISA KEV
- CISA SSVC: Exploitation none, automatable yes, technical impact total
- No public proof of concept found in the sources checked
Our recommendation
- Update Firefox and Thunderbird to 158.0.1 or later on all endpoints, including ESR installations
- Verify versions through your software inventory or RMM tool
- Re-check NVD and the Mozilla advisories for changes to scoring or fixed versions
- Treat as high priority given Mozilla's rating and the broad deployment of these products
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Mozilla advisory Firefox (MFSA 2026-111) www.mozilla.org
- Mozilla advisory Thunderbird (MFSA 2026-114) www.mozilla.org
- Mozilla Bugzilla bug 2079938 bugzilla.mozilla.org
- SUSE CVE record www.suse.com
- VulDB entry vuldb.com
- OpenCVE record app.opencve.io
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 30 Oct 2026, 17:23.
Original description (NVD)
Incorrect boundary conditions in the SVG component. This vulnerability was fixed in Firefox 158.0.1 and Thunderbird 158.0.1.
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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