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Mozilla Firefox EUVDEUVD-2026-88947

| CVE-2026-96869 MEDIUM
Information Exposure (CWE-200)
2026-09-29 mozilla GHSA-3vg3-56hv-p6hr
Information Disclosure Mozilla Firefox Suse
Medium
Disputed · 4.3 Vendor: mozilla
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Attack ChainAIDerived

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

  1. Access
    Lure victim to crafted page
  2. Exploit
    Victim's Firefox loads attacker content
  3. Execution
    Trigger Networking component flaw
  4. Impact
    Leak restricted information to attacker

Vulnerability Assessment

Weakness
CWE
CWE-200
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V14 - Data Protection Data exposure prevention
MITRE ATT&CK

2 techniques across 2 tactics: Collection, Discovery

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Requires user interaction (UI:R): the victim must actively load attacker-controlled web content in a vulnerable Firefox build (versions prior to Firefox 157, ESR 153.4, or ESR 140.17) for the flaw in the Networking component to trigger. No authentication or special privileges are needed on the attacker's side (PR:N), and default configurations are affected, but the mandatory user-interaction step and the limited confidentiality-only impact (no integrity/availability effect) materially constrain real-world risk. Impact is a bounded information leak, not code execution.
Impact

This is a genuinely low-priority issue despite affecting a ubiquitous product. The CVSS 3.1 score of 4.3 (Medium) is consistent with the provided vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N: network vector, low complexity, and no privileges required, but exploitation demands user interaction (UI:R) and yields only limited confidentiality impact (C:L) with no integrity or availability effect. No EPSS score, no CISA KEV listing, and no public POC were provided; Mozilla self-reported this via its own advisories (MFSA2026-97/99/100) and Bugzilla 2041248, which is the typical pipeline for coordinated Firefox fixes rather than active-exploitation disclosure. Exploitation status is therefore 'no public exploit identified at time of analysis.' The C:L rating indicates a bounded information leak in the Networking component (CWE-200), not memory-corruption RCE like sibling batch CVEs (e.g. CVE-2026-100768). No signals conflict: the network vector, low real-world exploitation likelihood, and modest impact all align. This is a high-prevalence-but-low-real-risk item - patch on normal cadence, not emergency.
Exploit ScenarioDerived

An attacker hosts a crafted web page and lures a victim running an unpatched Firefox into visiting it (UI:R). The page abuses the flaw in the Networking component to read a limited amount of information the attacker should not have access to (C:L), such as cross-origin or otherwise restricted data. No public exploit code was identified at time of analysis, and no authentication or elevated privileges are required of the attacker.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 29, 2026

Information disclosure in the Networking component of Mozilla Firefox can leak limited data to attacker-controlled content, but only after the victim loads a malicious page in a vulnerable build. The flaw affects Firefox versions prior to 157 and the ESR branches prior to 153.4 and 140.17, and can be triggered remotely without authentication (AV:N/AC:L/PR:N) because it requires only that the user interact with attacker-supplied web content (UI:R); impact is confined to low confidentiality loss with no integrity or availability effect. No public exploit code and no confirmed active exploitation were identified at time of analysis, and the resulting 4.3 CVSS score, combined with the mandatory user-interaction precondition, makes this a genuinely low-priority issue despite affecting a ubiquitous browser.

RemediationAI

Vendor-released patch: upgrade to Firefox 157 on the mainline release channel, or to Firefox ESR 153.4 or Firefox ESR 140.17 on the corresponding extended-support branches; Mozilla's advisories mfsa2026-100, mfsa2026-97, and mfsa2026-99 document these fixes, and the underlying change is tracked in Bugzilla bug 2041248. Because Firefox ships automatic background updates by default, most consumer installs will remediate on restart; managed fleets should push the ESR builds through their software distribution tooling or enterprise policy so that pinned or offline installations are not left behind, and should verify the running version rather than relying on the update channel alone. No product-level workaround is documented for this defect, and the mandatory user-interaction precondition cannot be engineered away from the client side. As compensating controls pending rollout, organizations can restrict browsing to trusted internal resources and limit exposure to untrusted web content through network egress filtering or a remote-browser-isolation layer - accepting the trade-off of reduced usability and potential breakage of legitimate web applications - while noting that disabling JavaScript or plugins would further shrink the attack surface but would break a large share of modern sites and is generally impractical. Given the low confidentiality-only impact and the absence of any public exploit or confirmed active exploitation at time of analysis, remediation should be scheduled at normal patch cadence rather than treated as an emergency.

Affects your stack

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Technical ContextAI · show details

The vulnerability resides in Firefox's Networking component - the in-browser stack that handles HTTP/HTTPS transactions, connection handling, caching, and related data flows between the browser and remote servers. Classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), the root cause is a logic or state-handling weakness that allows information to be released outside its intended boundary, rather than a memory-safety flaw such as a use-after-free that would enable code execution. The CPE entry cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* uses a wildcard version, meaning the defect is present across the entire pre-fix release history, including the two Extended Support Release channels; the fact that Mozilla issued fixes across three separate release trains (Firefox 157, Firefox ESR 153.4, and Firefox ESR 140.17) reflects the parallel mainline and long-term-support maintenance model in which enterprise and older-desktop deployments are patched through separate advisories. The CVSS vector (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N) confirms an unauthenticated network-reachable trigger that requires victim interaction and yields only a bounded, low-severity confidentiality leak within a single security scope, with no lateral impact on integrity or availability.

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Severity by source

Sources disagree (Medium–Critical)
Vendor (mozilla) PRIMARY 4.3 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
vuln.today AI 4.3 MEDIUM

Remote web-delivered flaw requiring a victim to visit a page (UI:R), no privileges (PR:N), yielding only a limited confidentiality leak (C:L) with no integrity or availability impact.

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

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 VectorVendor: mozilla

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

Lifecycle Timeline

3
CVSS changed
Sep 29, 2026 - 15:22 NVD
4.3 (MEDIUM)
CVE Published
Sep 29, 2026 - 12:36 cve.org
MEDIUM 4.3
CVE Published
Sep 29, 2026 - 12:36 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Information disclosure in the Networking component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

Threat Intelligence Overview

EPSS Score
0.2%
Top 90% exploitable
Prevalence
Ubiquitous
Firefox is one of the most widely deployed desktop browsers worldwide
Data Quality
6 sources
Confidence: High
EUVD 🇯🇵JVN 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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

22
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +22
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.

Affected Products (CPE)CVE.org

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

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Same weakness CWE-200 – Information Exposure

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CVE-2024-24919 HIGH POC
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Same technique Information Disclosure

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CVE-2025-68613 HIGH POC
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CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

SUSE

Severity: Critical
Product Status
Container suse/kiosk/firefox-esr:153.4-75.50 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Module for Desktop Applications 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-96869 ADVISORY https://vuldb.com/vuln/411364 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:23981/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4543/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:4545/ REF https://bugzilla.mozilla.org/show_bug.cgi?id=2041248 REF https://www.mozilla.org/security/advisories/mfsa2026-100/ REF https://www.mozilla.org/security/advisories/mfsa2026-101/ REF https://www.mozilla.org/security/advisories/mfsa2026-102/ REF https://www.mozilla.org/security/advisories/mfsa2026-103/ REF https://www.mozilla.org/security/advisories/mfsa2026-97/ REF https://www.mozilla.org/security/advisories/mfsa2026-99/

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