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CVE-2026-4692

Mozilla Firefox vulnerability

10.0 CRITICALEPSS 0.49%
  1. Published24 Mar 2026

Description

Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

Mozilla Firefox< 149.0 · ≥ 128.0 < 140.9.0 · < 115.34.0
Mozilla Thunderbird< 149.0 · < 140.9.0

Remediation

Fixed in
Mozilla Firefox≥ 149.0
Mozilla Thunderbird≥ 149.0

References

and 24 more references

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Frequently asked

Is CVE-2026-4692 being actively exploited?

CVE-2026-4692 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.49%.

How severe is CVE-2026-4692?

CVE-2026-4692 has a CVSS 3.1 base score of 10.0, rated critical. EPSS estimates a 0.49% probability of exploitation.

Which products are affected by CVE-2026-4692?

Affected products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2026-4692?

Upgrade affected software to a fixed version, for example Mozilla Firefox 149.0, Mozilla Thunderbird 149.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-4692 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.