Cyber Posture

CVE-2026-6777

Medium

Published: 21 April 2026

Published
21 April 2026
Modified
22 April 2026
KEV Added
Patch
CVSS Score 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS Score 0.0006 17.3th percentile
Risk Priority 11 60% EPSS · 20% KEV · 20% CVSS

Description

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

Likely Mitigating ControlsAI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-20 CWE-352

Security testing and developer training directly verify and enforce proper input validation, reducing exploitability of injection and malformed-data weaknesses.

addresses: CWE-20 CWE-400

Security testing and evaluation at multiple SDLC stages directly detects missing or flawed input validation, with the required remediation process ensuring fixes are applied.

addresses: CWE-400 CWE-352

Monitors for resource exhaustion and denial-of-service patterns that indicate uncontrolled consumption.

addresses: CWE-20 CWE-400

Spam protection mechanisms perform filtering and detection on inbound/outbound messages, directly compensating for missing or weak input validation of unsolicited content.

addresses: CWE-400

Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.

addresses: CWE-352

Awareness training educates users on avoiding untrusted links and actions that can be exploited via CSRF.

addresses: CWE-400

Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.

addresses: CWE-400

Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.

Security SummaryAI

CVE-2026-6777 is an unspecified vulnerability classified as "other issue" in the Networking: DNS component of Mozilla Firefox and Thunderbird. The flaw, associated with CWE-20 (Improper Input Validation), CWE-352 (Cross-Site Request Forgery), and CWE-400 (Uncontrolled Resource Consumption), carries a CVSS v3.1 base score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L), indicating medium severity with primary impact on availability.

Remote attackers can exploit this vulnerability over the network without authentication or user interaction, requiring low attack complexity. Successful exploitation results in a low-impact denial of service, such as resource exhaustion or service disruption, but does not compromise confidentiality or integrity.

Mozilla's security advisories (MFSA 2026-30 and MFSA 2026-33) and the associated Bugzilla entry (bug 2022726) confirm the issue was addressed in Firefox version 150 and Thunderbird version 150. Security practitioners should ensure affected users upgrade to these patched versions to mitigate the risk.

Details

CWE(s)

Affected Products

mozilla
firefox
≤ 150.0
mozilla
thunderbird
≤ 150.0

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
Why these techniques?

Vulnerability in client DNS handling (improper input validation + resource consumption) enables remote exploitation to trigger application-level denial of service via resource exhaustion.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1

References