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Mozilla Firefox CVE-2026-74973

| EUVDEUVD-2026-60668 MEDIUM
Use After Free (CWE-416)
2026-08-18 mozilla GHSA-cw58-8m9v-83jv
Information Disclosure Use After Free Memory Corruption Red Hat Mozilla Suse
4.2
CVSS 3.1 · Vendor: mozilla
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Attack ChainAIDerived

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

  1. Access
    Attacker hosts malicious web page
  2. Delivery
    User navigates to page in vulnerable Firefox
  3. Exploit
    Crafted content triggers race condition in Graphics component
  4. Execution
    Use-after-free accesses freed memory object
  5. Impact
    Limited heap data disclosed or browser memory corrupted

Vulnerability Assessment

Weakness
CWE
CWE-416
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

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Exploitation Conditions

User interaction is required - a user must actively navigate to an attacker-controlled or compromised web page (UI:R). The race condition imposes high attack complexity (AC:H): exploitation depends on winning a specific thread-scheduling timing window, making it non-deterministic and not automatable per SSVC assessment. No authentication or special privileges are required from the attacker's side (PR:N), but the vulnerability is scope-unchanged (S:U), confining any impact to the Firefox browser process itself rather than the underlying OS. There is no indication of a required non-default configuration - the Graphics component is active in standard Firefox operation. Exploitation is limited by: the need for user navigation to attacker content, the inherent non-reliability of race conditions across hardware and OS scheduler variations, and the absence of an availability impact component.
Impact

The CVSS 3.1 score of 4.2 (Medium) is well-supported by the vector components: high attack complexity (AC:H) due to the race condition's timing dependency, required user interaction (UI:R), and limited impact confined to the browser process (S:U, C:L, I:L, A:N). The SSVC framework independently corroborates this assessment - exploitation is rated 'none', the vector is not automatable, and technical impact is only 'partial'. No EPSS score was provided, but the combination of AC:H, UI:R, no KEV listing, and no known POC strongly suggests this is a low real-world exploitation priority despite being a memory corruption class vulnerability. Memory corruption bugs in browsers can sometimes be chained for higher impact, but no such chaining data is present in the available intelligence. This is a genuine patch-on-schedule item rather than an emergency response trigger.
Exploit ScenarioDerived

An attacker hosts a specially crafted web page containing content designed to trigger a race condition in Firefox's Graphics component - for example, rapidly creating and destroying graphics objects across threads while a rendering operation is in progress. When a user navigates to the page, the race window causes a freed object to be accessed, potentially leaking heap memory contents or corrupting adjacent data within the browser process. The timing-sensitive nature (AC:H) means reliable exploitation would require repeated attempts or precise environmental control, limiting opportunistic mass exploitation.
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 – Aug 18, 2026

Race condition and use-after-free memory corruption in Mozilla Firefox's Graphics component allows remote unauthenticated attackers to achieve limited confidentiality and integrity impact when a user visits a malicious web page. Affected across the standard release channel and all ESR branches, the vulnerability is fixed in Firefox 154, ESR 115.39, ESR 140.14, and ESR 153.1 per Mozilla's official advisories. No public exploit code has been identified and CISA has not listed this in KEV; the SSVC framework rates exploitation status as none and marks it not automatable.

RemediationAI

Upgrade to Mozilla Firefox 154 or later on the standard release channel. Organizations deploying Firefox ESR should upgrade to ESR 115.39, ESR 140.14, or ESR 153.1 depending on which ESR branch is in use. Full remediation details are in Mozilla Security Advisories mfsa2026-74 through mfsa2026-77 at https://www.mozilla.org/security/advisories/. No documented workarounds are available for this vulnerability. If immediate patching is not feasible, deploying browser isolation solutions (e.g., remote browser isolation proxies) or restricting user navigation to untrusted external sites can reduce attack surface, though these are operational compensating controls with usability trade-offs rather than technical fixes for the underlying memory management flaw.

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Technical ContextAI · show details

CWE-416 (Use After Free) identifies the root cause: a Graphics component object is freed during concurrent execution but subsequently dereferenced, creating a condition where stale or attacker-influenced memory may be read or written. The race condition qualifier indicates the flaw exists in multi-threaded rendering or compositing code, where object lifetime is not synchronized across threads - a class of bug common in browser GPU/graphics pipelines. The affected product is Mozilla Firefox across all versions (CPE: cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*), spanning both the standard release and ESR (Extended Support Release) channels. The tags 'Memory Corruption' and 'Information Disclosure' are consistent with typical use-after-free outcomes: read of freed memory can leak heap contents, while a write primitive could theoretically corrupt data structures.

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Severity by source

Vendor (mozilla) PRIMARY 4.2 MEDIUM
AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
vuln.today AI 4.2 MEDIUM

Race condition via malicious web page requires user navigation (UI:R) and precise timing (AC:H); no auth needed, impact limited to partial confidentiality and integrity within the browser process.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0 AV:N/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/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
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

2
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)
CVE Published
Aug 18, 2026 - 12:23 cve.org
MEDIUM 4.2

DescriptionCVE.org

Race condition, use-after-free in the Graphics component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.

Threat Intelligence Overview

EPSS Score
0.2%
Top 91% exploitable
Prevalence
Ubiquitous
globally dominant web browser across consumer and enterprise environments
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 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
High
Technical Impact
Partial

Priority Score

21
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +21
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Use After Free HIGH

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Memory Corruption HIGH

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

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-416 – Use After Free

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CVE-2017-0147 HIGH POC
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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

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-74973 ADVISORY https://vuldb.com/vuln/391630 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:3658/ REF https://bugzilla.mozilla.org/show_bug.cgi?id=2060357 REF https://www.mozilla.org/security/advisories/mfsa2026-74/ REF https://www.mozilla.org/security/advisories/mfsa2026-75/ REF https://www.mozilla.org/security/advisories/mfsa2026-76/ REF https://www.mozilla.org/security/advisories/mfsa2026-77/ REF https://www.mozilla.org/security/advisories/mfsa2026-78/ REF https://www.mozilla.org/security/advisories/mfsa2026-79/ REF https://www.mozilla.org/security/advisories/mfsa2026-80/

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