[UPDATE] [high] Mozilla Firefox: Multiple vulnerabilities
A remote, anonymous attacker can exploit multiple vulnerabilities in Mozilla Firefox to conduct unspecified attacks, potentially including code execution, bypassing security measures, disclosing or manipulating data, or causing Denial-of-Service conditions.
CSIRTS triage
- What
- Multiple vulnerabilities can be exploited to conduct unspecified attacks, potentially including code execution and data manipulation.
- Who is affected
- Users of Mozilla Firefox are affected.
- Urgency
- Remediation is urgent due to the high severity and potential for exploitation.
- Action
- Update to the latest version of Mozilla Firefox.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-1503
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-83880.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-83890.33% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 25% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-83900.50% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 40% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-83910.30% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 22% of all EPSS-scored CVEs.
- Low exploitation riskCVE-2026-84010.31% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 24% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-8388 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-8389 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-8390 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-8391 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-8401 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
Recent advisories for Mozilla Firefox
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- high[NEW] [high] Mozilla Firefox, Firefox ESR and Thunderbird: Multiple Vulnerabilitiescert-bund · 2026-08-25
- high[NEW] [high] Mozilla Firefox and Firefox ESR: Multiple vulnerabilitiescert-bund · 2026-08-18
- medium[NEW] [medium] Mozilla Firefox: Multiple vulnerabilities allow unspecified attackcert-bund · 2026-08-17
- high[UPDATE] [high] Mozilla Firefox, Firefox ESR and Thunderbird: Multiple vulnerabilitiescert-bund · 2026-08-17
- medium[NEW] [medium] Mozilla Firefox for Android: Vulnerability Enables Information Disclosurecert-bund · 2026-08-05
- unknownMozilla Firefox Information Disclosure Vulnerabilityhkcert · 2026-08-05
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