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Red Hat EUVDEUVD-2026-14851

| CVE-2026-4718 HIGH
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior (CWE-758)
2026-03-24 mozilla GHSA-9r85-xf24-6724
Information Disclosure Red Hat Mozilla Suse
High
Disputed · 8.1 NVD
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Attack ChainAIDerived

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

  1. Access
    User visits malicious webpage
  2. Delivery
    Webpage sends crafted WebRTC signaling message
  3. Exploit
    Undefined behavior triggered in signaling component
  4. Execution
    Memory corruption exploited
  5. Impact
    Attacker reads/modifies sensitive data

Vulnerability Assessment

Weakness
CWE
CWE-758
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Reliance on undefined/unspecified behavior
Exploitation Conditions

The victim must visit a malicious webpage or click a link while using Firefox versions below 149 (or Firefox ESR below 140.9). Requires user interaction. Remote attacker can exploit this without authentication.
Impact

The risk assessment for CVE-2026-4718 is complicated by missing CVSS and EPSS metrics. However, several factors indicate moderate to elevated concern: the undefined behavior classification in a network-exposed component (WebRTC signaling) suggests potential for exploitation via remote vectors with low complexity; the information disclosure tag indicates confirmed privacy impact; the rapid release of multiple security advisories (MFSA2026-20 and MFSA2026-22) suggests Mozilla prioritized this fix. Without CVSS vector data, we cannot determine privilege requirements or user interaction needs, but WebRTC is typically accessed through web content with minimal user friction. The lack of EPSS probability data and KEV status prevents full exploitation-likelihood assessment, but the assignment of two separate Mozilla advisories and disclosure via bug tracking systems suggests this was not an actively exploited zero-day. Real-world priority should remain high due to the information disclosure impact and broad Firefox user base, though it likely does not warrant emergency out-of-band patching if standard monthly update cycles are maintained.
Exploit ScenarioDerived

An attacker could craft a malicious webpage or establish a spoofed WebRTC peer connection that sends specially crafted signaling messages to trigger undefined behavior in the victim's Firefox browser. Upon loading the malicious page or accepting the peer connection, the browser's WebRTC signaling handler would process the crafted message, causing memory corruption that leaks sensitive information such as memory contents, session tokens, or cached credentials back to the attacker through side-channel observations or direct information disclosure channels. The attack requires only that the user visit a malicious website or accept a WebRTC connection request, making it suitable for watering-hole attacks or targeted malware distribution.
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

An undefined behavior vulnerability exists in the WebRTC Signaling component of Mozilla Firefox and Firefox ESR, potentially leading to information disclosure. This affects Firefox versions below 149 and Firefox ESR versions below 140.9. An attacker can exploit this through WebRTC signaling interactions to disclose sensitive information, though specific exploitation details remain limited in public disclosures.

RemediationAI

Users should upgrade Mozilla Firefox to version 149 or later, and Firefox ESR users should upgrade to version 140.9 or later. These updates are available through the standard Firefox update mechanism (Help > About Firefox or Edit > Preferences > General > Firefox Updates). Enterprise deployments using Firefox ESR should prioritize the ESR channel update to 140.9 to maintain extended support compatibility. Organizations managing Firefox deployments via Group Policy (Windows) or centralized configuration management should push these updates immediately. Until patching is complete, users can disable WebRTC in about:config by setting media.peerconnection.enabled to false, though this will break WebRTC-dependent applications and videoconferencing features. For sensitive environments, consider using Firefox in a sandboxed container or virtual machine until patches are verified to be installed across all systems.

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 WebRTC signaling protocol implementation within Firefox's media communication stack. WebRTC signaling is responsible for negotiating connection parameters, media codecs, and session establishment between peers. The undefined behavior classification suggests memory safety issues such as use-after-free, buffer overflows, or race conditions in signaling message processing. Firefox (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and Firefox ESR (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*) are affected across all platforms. While no specific CWE was assigned in the CVE record, undefined behavior in network signaling protocols typically falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) or CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization).

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Severity by source

Sources disagree (Low–High)
NVD PRIMARY 8.1 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
SUSE HIGH
Red Hat 3.4 LOW

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorNVD

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

Lifecycle Timeline

2
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
CVE Published
Mar 24, 2026 - 12:30 nvd
HIGH 8.1

DescriptionCVE.org

Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

CVE-2026-4718 presents notable security risk rated CVSS 8.1. Successful exploitation could significantly impact the confidentiality, integrity, or availability of affected systems. 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 100% exploitable
Data Quality
6 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
No
Human Impact
High
Technical Impact
Total

Priority Score

40
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +40
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.

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9.8
CVE-2026-4711 CRITICAL
9.8
CVE-2026-4723 CRITICAL
9.8

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CVE-2013-0753 CRITICAL POC
9.3 Jan 13

Use-after-free vulnerability in the serializeToStream implementation in the XMLSerializer component in Mozilla Firefox b
CVE-2012-3993 CRITICAL POC
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The Chrome Object Wrapper (COW) implementation in Mozilla Firefox before 16.0, Firefox ESR 10.x before 10.0.8, Thunderbi
CVE-2013-1710 CRITICAL POC
10.0 Aug 07

The crypto.generateCRMFRequest function in Mozilla Firefox before 23.0, Firefox ESR 17.x before 17.0.8, Thunderbird befo
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CVE-2013-0757 CRITICAL POC
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CVE-2014-1510 CRITICAL POC
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Same weakness CWE-758 – Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

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7.5

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-2026-4718 ADVISORY https://vuldb.com/?id.352766 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://bugzilla.mozilla.org/show_bug.cgi?id=2014864 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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