CVE-2026-6777 — Improper Input Validation in Mozilla Firefox

CWE-20 — Improper Input ValidationCWE-352 — Cross-Site Request ForgeryCWE-400 — Uncontrolled Resource ConsumptionCWE-676 — Use of Potentially Dangerous Function7 documents6 sources
Severity
5.3MEDIUMNVD
EPSS
0.1%
top 82.69%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Mozilla FirefoxMozilla Thunderbird
Timeline
PublishedApr 21
Latest updateApr 28

Description

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:LExploitability: 3.9 | Impact: 1.4

Affected Packages2 packages

▶Mozillamozilla/firefox< Firefox 150
▶Mozillamozilla/thunderbird< Thunderbird 150

🔴Vulnerability Details

2
VulDB
Mozilla Firefox up to 149 DNS Remote Code Execution (Nessus ID 310629)↗2026-04-28
▶
GHSA
GHSA-q3c8-p5vp-wr87: Other issue in the Networking: DNS component↗2026-04-21
▶

📋Vendor Advisories

3
Red Hat
Firefox: Firefox: Unspecified security flaw in Networking: DNS component↗2026-04-21
▶
Mozilla
Mozilla Foundation Security Advisory 2026-30: CVE-2026-6777↗
▶
Mozilla
Mozilla Foundation Security Advisory 2026-33: CVE-2026-6777↗
▶

💬Community

1
Bugzilla
CVE-2026-6777 Firefox: Firefox: Unspecified security flaw in Networking: DNS component↗2026-04-21
▶
CVE-2026-6777 — Improper Input Validation in Mozilla | cvebase