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Firefox ESR CVE-2026-8091

| EUVDEUVD-2026-28362 CRITICAL
Improper Check for Unusual or Exceptional Conditions (CWE-754)
2026-05-07 mozilla GHSA-jx5x-3wf9-9rhg
Mozilla Information Disclosure
9.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SUSE
CRITICAL
qualitative
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
May 09, 2026 - 01:32 vuln.today
CVSS changed
May 08, 2026 - 23:22 NVD
9.8 (CRITICAL)
CVE Published
May 07, 2026 - 12:45 nvd
UNKNOWN (no severity yet)
CVE Published
May 07, 2026 - 12:45 nvd
CRITICAL 9.8

DescriptionCVE.org

Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox ESR 140.10.2 and Firefox ESR 115.35.2.

AnalysisAI

Remote code execution in Firefox ESR allows unauthenticated network attackers to achieve complete system compromise via malformed audio/video content. Mozilla has released patches in Firefox ESR 140.10.2 and Firefox ESR 115.35.2. Despite a critical CVSS 9.8 score and SSVC rating of 'total' technical impact with automatable exploitation, EPSS assigns only 0.01% exploitation probability (1st percentile), and no public exploit or active exploitation has been identified. The severity stems from the unauthenticated network attack vector against a boundary condition flaw in media playback - a user-facing feature in a widely-deployed browser component.

Technical ContextAI

This vulnerability involves CWE-754 (Improper Check for Unusual or Exceptional Conditions) in the Firefox Audio/Video playback engine, which handles media content parsing and rendering. Boundary condition errors occur when code fails to validate input size, range, or format limits, potentially leading to buffer overflows, out-of-bounds reads/writes, or memory corruption. The CPE (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) identifies the Mozilla Firefox product line as affected, specifically the Extended Support Release (ESR) branches which enterprises and organizations use for stable, long-term deployments. Media playback components are complex attack surfaces that process untrusted data from web content, making them frequent targets for exploitation. The CVSS vector indicates this boundary condition can be triggered remotely without authentication or user interaction beyond normal browser operation.

RemediationAI

Immediately upgrade to Firefox ESR 140.10.2 (for ESR 140.x deployments) or Firefox ESR 115.35.2 (for ESR 115.x deployments) as confirmed by Mozilla Security Advisories MFSA2026-41 and MFSA2026-42 at https://www.mozilla.org/security/advisories/. For enterprise environments using managed deployment tools, prioritize this update in the next patch cycle given the critical CVSS score and complete system impact. If immediate patching is not feasible, implement defense-in-depth controls: disable autoplay for audio/video content via Firefox preferences (about:config → media.autoplay.default set to 5), deploy web filtering to block untrusted media-hosting domains, and restrict Firefox usage to known-safe internal sites only. Note that disabling media playback severely degrades user experience and is not sustainable long-term. Browser isolation technologies (remote browser isolation) can contain exploitation within sandboxed environments but introduce latency and complexity. No workaround fully mitigates the risk - patching is the only complete remediation.

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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise Server 12 SP5-LTSS Fixed
SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 Fixed
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Server 16.0 Affected
SUSE Linux Enterprise Desktop 15 SP7 Fixed

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CVE-2026-8091 vulnerability details – vuln.today
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