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Firefox Esr CVE-2026-4697

| EUVDEUVD-2026-14812 HIGH
Improper Check for Unusual or Exceptional Conditions (CWE-754)
2026-03-24 mozilla GHSA-8768-346v-cvr2
Information Disclosure Mozilla Firefox Esr
7.5
CVSS 3.1 · NVD
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Send crafted audio/video stream
  2. Exploit
    Trigger boundary condition error in Web Codecs
  3. Impact
    Cause denial of service via crash

Vulnerability Assessment

Weakness
CWE
CWE-754
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Unusual condition handling
Exploitation Conditions

Remote unauthenticated attacker can exploit Firefox versions below 149 (or ESR below 140.9) by delivering crafted audio/video content via network. No user interaction required. Affects default Firefox installations with Web Codecs enabled.
Impact

While specific CVSS, EPSS, and KEV metrics are not provided in the advisory data, the information disclosure classification and Mozilla's decision to issue multiple security advisories (MFSA2026-20 and MFSA2026-22) indicate this is a material security concern. The vulnerability affects widely-deployed consumer and enterprise software (Firefox and Firefox ESR), has a network-based attack vector (web content), and requires no user privileges beyond normal browsing. The absence of CVSS/EPSS data prevents quantitative risk scoring, but the combination of broad user base, low attack complexity (web-based exploitation), and information disclosure impact suggests this merits prompt patching. The boundary condition class of vulnerability is historically prone to exploitation once understood, and the fact that it affects codec processing—a common web activity—increases real-world exposure.
Exploit ScenarioDerived

An attacker creates a malicious website containing specially crafted audio or video content that triggers the boundary condition vulnerability in the Web Codecs component. When a victim visits the site using a vulnerable Firefox version, the browser processes the media, and the boundary condition error allows the attacker's code to read adjacent memory regions, potentially extracting sensitive data such as cached credentials, session tokens, or encryption keys. No special user interaction beyond visiting the webpage is required, as the vulnerability is triggered automatically during media codec processing.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

A boundary condition vulnerability exists in Firefox and Firefox ESR's Audio/Video Web Codecs component that allows information disclosure. The vulnerability affects Firefox versions prior to 149 and Firefox ESR versions prior to 140.9. An attacker can exploit this flaw to disclose sensitive information, potentially leveraging web-based attack vectors without requiring elevated privileges.

RemediationAI

Immediately upgrade Firefox to version 149 or later, and Firefox ESR to version 140.9 or later. Both upgrades are available through the automatic update mechanism in the browser (Help > About Firefox will check for and install updates). Users in managed environments should deploy these updates via their standard patch management processes. Until patching is complete, users can reduce exposure by disabling media playback where possible, avoiding untrusted websites with embedded audio/video content, and ensuring their browser is kept in a restricted security context (e.g., running with minimal extensions and in a sandbox where available). The Mozilla security advisories at https://www.mozilla.org/security/advisories/mfsa2026-20/ and https://www.mozilla.org/security/advisories/mfsa2026-22/ provide official confirmation and additional context.

Affected VersionsENISA

Firefox unspecified <149
Firefox ESR unspecified <140.9

Affected Packages

euvd firefox_esr_unspecified fix: 140.9
euvd firefox_unspecified fix: 149

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

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Technical ContextAI · show details

The vulnerability resides in the Audio/Video Web Codecs implementation within Mozilla Firefox (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* and cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*), which handles multimedia codec operations in web contexts. The root cause is classified as an incorrect boundary condition, meaning the code fails to properly validate or enforce limits on memory access, buffer indices, or data structure boundaries during codec processing. This type of vulnerability (boundary condition error) typically allows attackers to read memory outside intended regions, leading to information disclosure of sensitive data such as encryption keys, credentials, or other process memory contents.

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Severity by source

NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE HIGH
Red Hat 7.5 HIGH

Primary rating from NVD.

CVSS VectorNVD

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

Lifecycle Timeline

2
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
CVE Published
Mar 24, 2026 - 12:30 nvd
HIGH 7.5

DescriptionNVD

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

CVE-2026-4697 presents notable security risk rated CVSS 7.5. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and consider compensating controls in the interim.

Business Impact: High
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score
0.0%
Top 97% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

38
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Related Vulnerabilities in Firefox Multiple Memory and Boundary Vulnerabilities

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CVE-2026-4707 HIGH
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CVE-2026-4710 CRITICAL
9.8
CVE-2026-4711 CRITICAL
9.8
CVE-2026-4723 CRITICAL
9.8

More in Firefox Esr

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3.7 May 21

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In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable

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A sandbox escape vulnerability exists in Firefox's XPCOM component due to incorrect boundary conditions and integer over
CVE-2022-29917 CRITICAL POC
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Mozilla developers Andrew McCreight, Gabriele Svelto, Tom Ritter and the Mozilla Fuzzing Team reported memory safety bug
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7.5 Sep 25

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CVE-2022-26384 CRITICAL POC
9.6 Dec 22

If an attacker could control the contents of an iframe sandboxed with <code>allow-popups</code> but not <code>allow-scri
CVE-2022-34484 HIGH POC
8.8 Dec 22

The Mozilla Fuzzing Team reported potential vulnerabilities present in Thunderbird 91.10. Rated high severity (CVSS 8.8)
CVE-2022-28281 HIGH POC
8.8 Dec 22

If a compromised content process sent an unexpected number of WebAuthN Extensions in a Register command to the parent pr
CVE-2022-26381 HIGH POC
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An attacker could have caused a use-after-free by forcing a text reflow in an SVG object leading to a potentially exploi
CVE-2022-22756 HIGH POC
8.8 Dec 22

If a user was convinced to drag and drop an image to their desktop or other folder, the resulting object could have been
CVE-2022-22740 HIGH POC
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Certain network request objects were freed too early when releasing a network request handle. Rated high severity (CVSS

CVE-2022-22738 HIGH POC
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Applying a CSS filter effect could have accessed out of bounds memory. Rated high severity (CVSS 8.8), this vulnerabilit

Same weakness CWE-754 – Improper Check for Unusual or Exceptional Conditions

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Same technique Information Disclosure

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Vendor StatusVendor

Debian

firefox
Release Status Fixed Version Urgency
sid vulnerable 148.0.2-1 -
(unstable) fixed (unfixed) -
firefox-esr
Release Status Fixed Version Urgency
bullseye vulnerable 115.14.0esr-1~deb11u1 -
bullseye (security) vulnerable 140.8.0esr-1~deb11u1 -
bookworm vulnerable 128.14.0esr-1~deb12u1 -
bookworm (security) vulnerable 140.8.0esr-1~deb12u1 -
trixie (security), trixie vulnerable 140.8.0esr-1~deb13u1 -
forky, sid vulnerable 140.8.0esr-1 -
(unstable) fixed (unfixed) -

SUSE

Severity: High
Product Status
Image SLES15-SP5-SAP-Azure-LI-BYOS Image SLES15-SP5-SAP-Azure-LI-BYOS-Production Image SLES15-SP5-SAP-Azure-VLI-BYOS Image SLES15-SP5-SAP-Azure-VLI-BYOS-Production Image SLES15-SP6-SAP-Azure-LI-BYOS Image SLES15-SP6-SAP-Azure-LI-BYOS-Production Image SLES15-SP6-SAP-Azure-VLI-BYOS Image SLES15-SP6-SAP-Azure-VLI-BYOS-Production Image SLES15-SP7-SAP-Azure-LI-BYOS-Production Image SLES15-SP7-SAP-Azure-VLI-BYOS-Production Affected
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:5930 ADVISORY https://access.redhat.com/errata/RHSA-2026:5931 ADVISORY https://access.redhat.com/errata/RHSA-2026:5932 ADVISORY https://access.redhat.com/errata/RHSA-2026:6188 ADVISORY https://access.redhat.com/errata/RHSA-2026:6342 ADVISORY https://access.redhat.com/errata/RHSA-2026:6917 ADVISORY https://access.redhat.com/errata/RHSA-2026:7837 ADVISORY https://access.redhat.com/errata/RHSA-2026:7838 ADVISORY https://access.redhat.com/errata/RHSA-2026:7839 ADVISORY https://access.redhat.com/errata/RHSA-2026:7840 ADVISORY https://access.redhat.com/errata/RHSA-2026:7841 ADVISORY https://access.redhat.com/errata/RHSA-2026:7842 ADVISORY https://access.redhat.com/errata/RHSA-2026:7843 ADVISORY https://access.redhat.com/errata/RHSA-2026:7845 ADVISORY https://access.redhat.com/errata/RHSA-2026:7858 ADVISORY https://access.redhat.com/errata/RHSA-2026:8284 ADVISORY https://access.redhat.com/errata/RHSA-2026:8285 ADVISORY https://access.redhat.com/errata/RHSA-2026:8286 ADVISORY https://access.redhat.com/errata/RHSA-2026:8287 ADVISORY https://access.redhat.com/errata/RHSA-2026:8288 ADVISORY https://access.redhat.com/errata/RHSA-2026:8289 ADVISORY https://access.redhat.com/errata/RHSA-2026:8290 ADVISORY https://access.redhat.com/errata/RHSA-2026:8315 ADVISORY https://access.redhat.com/errata/RHSA-2026:8427 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-4697 ADVISORY https://vuldb.com/?id.352746 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1126/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1127/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1163/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20978/ REF https://access.redhat.com/errata/RHSA-2026:8850 REF https://access.redhat.com/security/cve/CVE-2026-4697 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2020422 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450729 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4697.json REF https://www.mozilla.org/security/advisories/mfsa2026-20/ REF https://www.mozilla.org/security/advisories/mfsa2026-22/ REF https://www.mozilla.org/security/advisories/mfsa2026-23/ REF https://www.mozilla.org/security/advisories/mfsa2026-24/

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