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CVE-2026-4692

Mozilla Firefox, Thunderbird, Red Hat Enterprise Linux 10

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
10
EPSS
0.49%
39.3% percentile
CISA KEV
Not listed
Published
2026.03.24
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.49%
Technical severityCVSS 10

Vulnerability overview

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.

Affected product and versions

Product
Mozilla Firefox, Thunderbird, Red Hat Enterprise Linux 10
Affected versions
< 115.34.0, < 149.0, >= 128.0 < 140.9.0, < 140.9.0
Fixed versions
115.34.0, 149.0, 140.9.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Mozilla Firefox, Thunderbird, Red Hat Enterprise Linux 10 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CWE
CWE-653
CVE-2026-4692 — Mozilla Firefox, Thunderbird, Red Hat Enterprise Linux 10 | SECUFOCUS NOW