Skip to main content

Mozilla Firefox EUVDEUVD-2026-60757

| CVE-2026-74957 HIGH
Protection Mechanism Failure (CWE-693)
2026-08-18 mozilla GHSA-w4xm-w4c4-5fhg
8.1
CVSS 3.1 · Vendor: mozilla
View

Attack ChainAIDerived

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

  1. Access
    Attacker registers phishing or malware-hosting URL
  2. Delivery
    Crafts navigation sequence exploiting Safe Browsing bypass
  3. Exploit
    Victim clicks or follows attacker-supplied link
  4. Execution
    Firefox skips Safe Browsing interstitial
  5. Persist
    Victim lands on unblocked malicious page
  6. Impact
    Credentials phished or malware delivered

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V15 - Secure Coding and Architecture Protection mechanism completeness
Exploitation Conditions

User interaction is required - the CVSS UI:R metric confirms the victim must actively navigate to or click a link leading to the malicious URL. The vulnerable Safe Browsing component is enabled by default in all Firefox installations, so no non-default configuration is needed on the victim side. Exploitation is limited to scenarios where the target URL would normally be intercepted by Safe Browsing; benign URLs are unaffected. The attacker must control or predict a URL that Safe Browsing would ordinarily flag, meaning the malicious site or URL pattern must already be (or be likely to be) present in Safe Browsing blocklists. Authentication is not relevant to exploitation - the CVSS PR:N vector confirms no privilege level is required on the attacker side.

Impact

The CVSS 8.1 vector (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N) reflects meaningful theoretical impact: network-reachable, low complexity, no privileges required, but requiring user interaction. The High ratings for both Confidentiality and Integrity capture the downstream consequence of a successful Safe Browsing bypass - credential phishing and malware delivery are the primary threat scenarios. However, EPSS at 0.16% (6th percentile) strongly undercuts urgency: at time of analysis, this vulnerability has extremely low observed exploitation probability relative to the broader CVE population. There is no CISA KEV listing and no confirmed public exploit code. The gap between CVSS 8.1 and the near-floor EPSS score is notable and suggests this is a high-CVSS-but-low-real-risk issue in practice - the complexity of reliably triggering the bypass in deployed conditions may be higher than AC:L implies, or attacker tooling has not yet emerged. UI:R is a meaningful friction point, as it requires a victim to actively follow a crafted link. This is a patch-priority item for browser hygiene, not an emergency incident-response trigger.

Exploit ScenarioDerived

An attacker registers or compromises a domain that Firefox's Safe Browsing service has flagged as a phishing or malware host. By exploiting the bypass, the attacker crafts a URL or navigation sequence that causes Firefox to skip the Safe Browsing interstitial, delivering the user directly to the malicious page. The victim, expecting browser-level protection, proceeds to interact with the phishing page and submits credentials or downloads a malicious payload without any browser warning. No public exploit code has been identified at time of analysis.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.2% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAIv1 – Aug 21, 2026

Safe Browsing mitigation bypass in Mozilla Firefox allows a remote unauthenticated attacker (with user interaction) to circumvent Firefox's phishing and malware URL-blocking protections, classified under CWE-693 (Protection Mechanism Failure). Affected versions span all Firefox releases prior to 154 and all ESR branches prior to 140.14 and 153.1, giving this a broad blast radius across consumer and enterprise deployments. No public exploit code has been identified and EPSS sits at 0.16% (6th percentile), indicating low observed exploitation activity despite the high CVSS score of 8.1.

RemediationAI

Vendor-released patch: Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1. Administrators should upgrade to the appropriate fixed release for their deployment track immediately. Enterprise environments pinned to ESR should target ESR 140.14 or ESR 153.1 depending on their current ESR branch. The primary advisory references are https://www.mozilla.org/security/advisories/mfsa2026-74/, https://www.mozilla.org/security/advisories/mfsa2026-76/, https://www.mozilla.org/security/advisories/mfsa2026-77/, and https://www.mozilla.org/security/advisories/mfsa2026-78/. Bugzilla tracking is at https://bugzilla.mozilla.org/show_bug.cgi?id=2041906. If patching is immediately infeasible, a compensating control is to enforce network-layer DNS or proxy-based URL filtering (e.g., Cisco Umbrella, Cloudflare Gateway) to replicate safe-browsing-style blocking outside the browser process - this adds operational overhead and may introduce latency but removes dependence on the in-browser Safe Browsing check. Disabling JavaScript or enabling strict content security policies for untrusted sites does not mitigate this class of bypass, as it operates at the navigation layer, not the script layer.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The Safe Browsing component in Firefox implements real-time URL checking against blocklists of known phishing domains, malware distribution sites, and social engineering pages. CWE-693 (Protection Mechanism Failure) describes the root cause: the protective control itself is defeated or circumvented rather than bypassed through a logic flaw in application business logic. In Firefox's implementation, Safe Browsing acts as a pre-navigation gate; a bypass means crafted URLs or navigation sequences can reach the rendering engine without triggering the expected interstitial warning pages. The CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* confirms that all Firefox application builds across all platforms are in scope prior to the fixed versions, not just specific OS variants. The breadth of advisory coverage (mfsa2026-74, -76, -77, -78, -79, -80) suggests the fix was applied across multiple release trains simultaneously.

Know when Mozilla gets its next vulnerability

  • Watch products and get an email when something new is published
  • Check this CVE against your own stack and servers
  • Exploit and PoC references, threat intelligence from 22 sources

No credit card · 7-day full trial

Severity by source

Vendor (mozilla) PRIMARY 8.1 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
vuln.today AI 8.1 HIGH

Network-delivered bypass requiring user navigation; no privileges needed; High C and I reflect phishing credential theft and malware delivery; no availability impact applies.

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

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

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

Lifecycle Timeline

3
CVSS changed
Aug 21, 2026 - 20:22 NVD
8.1 (HIGH)
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)
CVE Published
Aug 18, 2026 - 12:23 cve.org
HIGH 8.1

DescriptionCVE.org

Mitigation bypass in the Safe Browsing component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Executive ViewAI

Why It Matters

Mozilla Firefox versions prior to 154 (and ESR versions prior to 140.14/153.1) contain a bypass of the Safe Browsing protection mechanism that defends users against phishing and malware URLs. An unauthenticated attacker can craft malicious links that circumvent Firefox's built-in protections, increasing organizational exposure to credential theft and malware delivery through social engineering attacks. This core security control bypass affects widely-deployed Firefox installations and requires immediate interim mitigation despite currently low observed exploitation.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: deploy URL filtering and web gateway controls blocking known malicious domains; enforce DNS-level protection with current threat intelligence feeds; implement email security controls to prevent phishing link delivery; conduct security awareness training on link verification practices; restrict Firefox use for high-risk activities (financial transactions, credential entry, administrative access) until patched; monitor endpoint detection and response (EDR) platforms for exploitation attempts; maintain accurate Firefox version inventory to enable rapid patch deployment when available.

Threat Intelligence Overview

EPSS Score
0.2%
Top 94% exploitable
Prevalence
High
major web browser with hundreds of millions of active users
Data Quality
6 sources
Confidence: High

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 0.2%
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· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact
High

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

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)CVE.org

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
CVE-2015-4495 HIGH POC
8.8 Aug 08

The PDF reader in Mozilla Firefox before 39.0.3, Firefox ESR 38.x before 38.1.1, and Firefox OS before 2.2 allows remote

CVE-2013-1690 HIGH POC
8.8 Jun 26

Mozilla Firefox before 22.0, Firefox ESR 17.x before 17.0.7, Thunderbird before 17.0.7, and Thunderbird ESR 17.x before

CVE-2013-0758 CRITICAL POC
9.3 Jan 13

Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and 17.x before 17.0.2, Thunderbird before 17.0.2, Thunderb

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
9.3 Oct 10

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

CVE-2017-3823 HIGH POC
8.8 Feb 01

An issue was discovered in the Cisco WebEx Extension before 1.0.7 on Google Chrome, the ActiveTouch General Plugin Conta

CVE-2014-8636 HIGH POC
7.5 Jan 14

The XrayWrapper implementation in Mozilla Firefox before 35.0 and SeaMonkey before 2.32 does not properly interact with

CVE-2013-0757 CRITICAL POC
9.3 Jan 13

The Chrome Object Wrapper (COW) implementation in Mozilla Firefox before 18.0, Firefox ESR 17.x before 17.0.2, Thunderbi

CVE-2014-1510 CRITICAL POC
9.8 Mar 19

The Web IDL implementation in Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and Se

CVE-2014-1511 CRITICAL POC
9.8 Mar 19

Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and SeaMonkey before 2.25 allow remo

CVE-2013-0643 HIGH
8.8 Feb 27

The Firefox sandbox in Adobe Flash Player before 10.3.183.67 and 11.x before 11.6.602.171 on Windows and Mac OS X, and b

Vendor StatusVendor

SUSE

Severity: Important
Product Status
Container suse/kiosk/firefox-esr:140.14-75.12 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 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

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy