How severe is CVE-2026-12294?

CVE-2026-12294 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-12294 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-12294?

CVE-2026-12294 primarily affects Mozilla Firefox. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-12294?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-12294 have an EU (EUVD) identifier?

Yes. CVE-2026-12294 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-37085.

When was CVE-2026-12294 published?

CVE-2026-12294 was published on 2026-06-16 and last updated on 2026-07-07.

CVE-2026-12294

CVE-2026-12294 is a critical-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 9.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-693.

Key facts

Severity: Critical (CVSS 3.x base score 9.6)
EPSS exploit prediction: 0% (28th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-37085
Weakness: CWE-693
Affected product: Mozilla Firefox
Published: 2026-06-16
Last modified: 2026-07-07

Description

Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

Frequently asked questions

What is CVE-2026-12294?: Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
How severe is CVE-2026-12294?: CVE-2026-12294 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-12294 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-12294?: CVE-2026-12294 primarily affects Mozilla Firefox. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-12294?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-12294 have an EU (EUVD) identifier?: Yes. CVE-2026-12294 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-37085.
When was CVE-2026-12294 published?: CVE-2026-12294 was published on 2026-06-16 and last updated on 2026-07-07.

References

Affected products (4)

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

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