How severe is CVE-2026-0878?

CVE-2026-0878 has a CVSS 3.x base score of 8.0, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-0878 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-0878?

CVE-2026-0878 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-2026-0878?

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

Does CVE-2026-0878 have an EU (EUVD) identifier?

Yes. CVE-2026-0878 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2340.

When was CVE-2026-0878 published?

CVE-2026-0878 was published on 2026-01-13 and last updated on 2026-06-30.

CVE-2026-0878

CVE-2026-0878 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 8.0. 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-20.

Key facts

Severity: High (CVSS 3.x base score 8.0)
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-2340
Weakness: CWE-20
Affected product: Mozilla Firefox
Published: 2026-01-13
Last modified: 2026-06-30

Description

Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

Frequently asked questions

What is CVE-2026-0878?: Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
How severe is CVE-2026-0878?: CVE-2026-0878 has a CVSS 3.x base score of 8.0, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-0878 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-0878?: CVE-2026-0878 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-2026-0878?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-0878 have an EU (EUVD) identifier?: Yes. CVE-2026-0878 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2340.
When was CVE-2026-0878 published?: CVE-2026-0878 was published on 2026-01-13 and last updated on 2026-06-30.

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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