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Mozilla Firefox CVE-2026-6763

| EUVDEUVD-2026-24104 MEDIUM
Protection Mechanism Failure (CWE-693)
2026-04-21 mozilla GHSA-jgph-c6j5-5mm2
Authentication Bypass Mozilla
6.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
6.5 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
vuln.today AI
5.4 MEDIUM

Browser file-handling bypasses realistically require user-triggered file interaction, justifying UI:R over the provided UI:N, which also resolves the SSVC Automatable:no conflict.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative
Red Hat
6.1 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

5
Analysis Generated
Jul 24, 2026 - 07:10 vuln.today
Patch released
Apr 29, 2026 - 02:30 nvd
Patch available
CVSS changed
Apr 21, 2026 - 21:22 NVD
6.5 (None) 6.5 (MEDIUM)
EUVD ID Assigned
Apr 21, 2026 - 13:15 euvd
EUVD-2026-24104
CVE Published
Apr 21, 2026 - 12:40 nvd
MEDIUM 6.5

DescriptionCVE.org

Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 150 and Firefox ESR 140.10.

AnalysisAI

Mitigation bypass in Mozilla Firefox's File Handling component allows remote network-reachable attackers to circumvent a security protection mechanism (CWE-693), resulting in partial confidentiality and integrity compromise. All Firefox stable versions prior to 150 and Firefox ESR versions prior to 140.10 are affected across platforms, with downstream impact confirmed for Red Hat Enterprise Linux and SUSE Linux packaging. No active exploitation has been confirmed - CISA KEV listing is absent, EPSS sits at 0.04% (12th percentile), and SSVC classifies exploitation status as none - making this a medium-priority patching item rather than an emergency response trigger.

Technical ContextAI

CWE-693 (Protection Mechanism Failure) describes a vulnerability class where a security control - such as a sandbox boundary, content-type enforcement policy, or file download safety check - fails to operate as intended, allowing an attacker to sidestep it rather than overcome it directly. In Firefox's File Handling component, this likely involves the browser's processing of file resources in a way that circumvents an existing mitigation layer. CPE data (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) indicates all Firefox versions across all platforms are in scope. The simultaneous fix in both Firefox 150 (standard release) and ESR 140.10 (extended support release) - with four separate Mozilla advisories published (mfsa2026-30, mfsa2026-32, mfsa2026-33, mfsa2026-34) - indicates coordinated disclosure across release tracks. The Bugzilla ticket at bug 2021666 was filed internally by Mozilla, consistent with internal security research discovery.

RemediationAI

The primary remediation is upgrading Firefox to version 150 or later on the standard release channel, or to Firefox ESR 140.10 or later on the extended support release channel. Mozilla's official security advisories for this issue are at https://www.mozilla.org/security/advisories/mfsa2026-30/ and https://www.mozilla.org/security/advisories/mfsa2026-32/. Red Hat Enterprise Linux users should apply the applicable errata: RHSA-2026:10767, RHSA-2026:10766, or RHSA-2026:10757 (https://access.redhat.com/errata/). SUSE users should consult their respective SUSE security advisory for updated Firefox packages. If patching cannot be applied immediately, network-level controls restricting browser-based file downloads or enforcing content inspection proxies may reduce exposure surface, but these controls carry operational trade-offs including broken legitimate file download workflows and do not eliminate the underlying mitigation bypass.

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Same weakness CWE-693 – Protection Mechanism Failure

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Server 16.0 SUSE Linux Enterprise Server for SAP applications 16.0 Fixed
openSUSE Leap 16.0 Fixed

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CVE-2026-6763 vulnerability details – vuln.today
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