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Mozilla Firefox EUVDEUVD-2026-60750

| CVE-2026-74943 CRITICAL
Use After Free (CWE-416)
2026-08-18 mozilla GHSA-cx5v-35ww-82cj
Information Disclosure Use After Free Memory Corruption Red Hat Mozilla Suse
9.8
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Host crafted image on web page
  2. Delivery
    Lure victim to load page
  3. Exploit
    Firefox ImageLib decodes malformed image
  4. Execution
    Trigger use-after-free on freed surface
  5. Persist
    Groom heap for controlled reuse
  6. Impact
    Leak memory or execute code in content process

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

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

Exploitation requires the victim's Firefox to decode attacker-supplied image data through the ImageLib component - i.e., the user must visit a malicious or compromised page, open an HTML email that auto-loads images, or otherwise load the crafted image; this user-interaction requirement is the primary limiting factor and contradicts the published UI:N metric. No authentication is needed against the browser (PR:N per CVSS), and no non-default configuration is required since image decoding is enabled by default. Reliable code execution (versus a memory-disclosure-only outcome) additionally depends on defeating content-process sandboxing and ASLR, raising practical attack complexity.
Impact

The signals conflict and should be read carefully. NVD scores this 9.8 CRITICAL with AV:N/AC:L/PR:N/UI:N, but that vector is optimistic for a browser image-parsing bug: real exploitation requires the victim to load a page or image, which is user interaction (UI:R) not captured in the published vector - verify against Mozilla's advisory. EPSS is only 0.20% (10th percentile) and there is no KEV listing and no known POC, so despite the CRITICAL rating this is not evidence of active or imminent mass exploitation. That said, ImageLib UAFs are a historically productive class for browser exploit chains, so the technical severity is genuine even if the near-term probability is low. Net: patch promptly as part of normal browser update cadence, but this does not warrant emergency out-of-band response absent new exploitation evidence.
Exploit ScenarioDerived

An attacker hosts a web page embedding a specially crafted image, or injects such an image into a site or ad network the victim visits. When Firefox's ImageLib decodes the malformed image it triggers the use-after-free, letting the attacker leak adjacent heap memory or, chained with heap grooming, corrupt memory toward code execution in the content process. No public exploit is currently identified, and successful exploitation requires the victim to load the malicious content.
Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 20, 2026

Memory corruption via a use-after-free in Firefox's Graphics: ImageLib component allows a remote attacker to potentially execute code or disclose memory contents when a victim renders attacker-controlled image data. All Firefox channels are affected up to the fixed builds (Firefox 154 and ESR 115.39, 140.14, 153.1). No public exploit identified at time of analysis, and EPSS is low (0.20%, 10th percentile), indicating no observed weaponization despite the high CVSS score.

RemediationAI

Vendor-released patch: upgrade to Firefox 154, or to Firefox ESR 115.39, ESR 140.14, or ESR 153.1 depending on your deployed ESR line, per Mozilla advisories mfsa2026-74 through mfsa2026-80 (https://www.mozilla.org/security/advisories/mfsa2026-74/). For managed fleets, push the update through enterprise policy or your software-distribution system and confirm the ESR branch matches your support baseline. As an interim compensating control where patching lags, you can reduce exposure by disabling image loading or forcing images off by default (permissions.default.image=2), which blocks the vulnerable decode path but breaks most modern web pages, or by restricting browsing to trusted sites via proxy allowlisting; both are disruptive and are stopgaps only until the patched build is deployed.

Affects your stack

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Technical ContextAI · show details

The flaw is a CWE-416 use-after-free in ImageLib, Firefox's image-decoding subsystem within the Graphics layer, which parses and rasterizes formats such as PNG, JPEG, GIF, WebP and AVIF encountered on web pages. A use-after-free occurs when the decoder frees a heap object (e.g., an image frame or surface buffer) but retains and later dereferences a dangling pointer, letting an attacker who controls heap layout influence what data occupies the freed region. The single affected CPE is cpe:2.3:a:mozilla:firefox, and the tag set (Use After Free, Memory Corruption, Information Disclosure) reflects both the read-primitive (leaking adjacent heap memory) and the write/execution potential typical of image-parser UAFs in browsers.

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Severity by source

NVD PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 7.5 HIGH

Remote via crafted image but requires the victim to load content (UI:R) and reliable UAF exploitation needs heap grooming/sandbox defeat (AC:H); full C/I/A impact within the content process.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
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
High
Integrity
High
Availability
High

Lifecycle Timeline

3
CVSS changed
Aug 20, 2026 - 20:37 NVD
9.8 (CRITICAL)
CVE Published
Aug 18, 2026 - 12:23 nvd
CRITICAL 9.8
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)

DescriptionNVD

Use-after-free in the Graphics: ImageLib component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.

Executive ViewAI

Why It Matters

Firefox installations across all supported channels contain a critical use-after-free vulnerability (CVE-2026-74943) enabling remote code execution through maliciously crafted images. No public exploit identified at time of analysis (EPSS 0.2%), but Firefox's ubiquitous enterprise deployment means organizations must implement immediate defensive measures and prepare for rapid patch deployment once available.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations include: deploy Content Security Policy restricting image sources; implement browser configuration policies disabling JavaScript in untrusted contexts; block known malicious domains at network perimeter; monitor for suspicious browser crashes and rendering anomalies; implement process sandboxing for Firefox; provide user security training on avoiding suspicious images and untrusted websites.

Threat Intelligence Overview

EPSS Score
0.2%
Top 90% exploitable
Prevalence
High
major mainstream web browser deployed across enterprise and consumer endpoints
Data Quality
4 sources
Confidence: Medium
EUVD NVD CVE.org EPSS 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 CRITICAL
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
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
Yes
Human Impact
High

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +49
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)NVD

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

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Same weakness CWE-416 – Use After Free

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CVE-2019-0708 CRITICAL POC
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Same technique Information Disclosure

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CVE-2025-68613 HIGH POC
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CVE-2015-1701 HIGH POC
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CVE-2017-0147 HIGH POC
7.5

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-2026-74943 ADVISORY https://vuldb.com/vuln/391594 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:3658/ REF https://bugzilla.mozilla.org/show_bug.cgi?id=2057308 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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