How severe is CVE-2026-6777?

CVE-2026-6777 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-6777 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-6777?

CVE-2026-6777 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-6777?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-6777 have an EU (EUVD) identifier?

Yes. CVE-2026-6777 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24118.

When was CVE-2026-6777 published?

CVE-2026-6777 was published on 2026-04-21 and last updated on 2026-06-17.

CVE-2026-6777

CVE-2026-6777 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 5.3. 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: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (6th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-24118
Weakness: CWE-20
Affected product: Mozilla Firefox
Published: 2026-04-21
Last modified: 2026-06-17

Description

Other issue in the Networking: DNS component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.

Frequently asked questions

What is CVE-2026-6777?: Other issue in the Networking: DNS component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
How severe is CVE-2026-6777?: CVE-2026-6777 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-6777 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6777?: CVE-2026-6777 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-6777?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-6777 have an EU (EUVD) identifier?: Yes. CVE-2026-6777 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24118.
When was CVE-2026-6777 published?: CVE-2026-6777 was published on 2026-04-21 and last updated on 2026-06-17.

References

Affected products (2)

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

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