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    CVE-2026-74934

    Site isolation issue in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

    Published:Aug 18, 2026
    Last Modified:Aug 24, 2026
    EPS:Aug 18, 2026
    EPSS Score:0.00168
    CVSS Score:7.5

    Affected Products

    Vendor
    Mozilla
    Product
    Firefox
    Vendor
    Mozilla
    Product
    Thunderbird

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-111 JSON Hijacking (aka JavaScript Hijacking)
    CAPEC-116 Excavation
    CAPEC-13 Subverting Environment Variable Values
    CAPEC-141 Cache Poisoning
    CAPEC-142 DNS Cache Poisoning
    CAPEC-160 Exploit Script-Based APIs
    CAPEC-169 Footprinting
    CAPEC-19 Embedding Scripts within Scripts
    CAPEC-21 Exploitation of Trusted Identifiers
    CAPEC-22 Exploiting Trust in Client
    CAPEC-224 Fingerprinting
    CAPEC-285 ICMP Echo Request Ping
    CAPEC-287 TCP SYN Scan
    CAPEC-290 Enumerate Mail Exchange (MX) Records
    CAPEC-291 DNS Zone Transfers
    CAPEC-292 Host Discovery
    CAPEC-293 Traceroute Route Enumeration
    CAPEC-294 ICMP Address Mask Request
    CAPEC-295 Timestamp Request
    CAPEC-296 ICMP Information Request
    CAPEC-297 TCP ACK Ping
    CAPEC-298 UDP Ping
    CAPEC-299 TCP SYN Ping
    CAPEC-300 Port Scanning
    CAPEC-301 TCP Connect Scan
    CAPEC-302 TCP FIN Scan
    CAPEC-303 TCP Xmas Scan
    CAPEC-304 TCP Null Scan
    CAPEC-305 TCP ACK Scan
    CAPEC-306 TCP Window Scan
    CAPEC-307 TCP RPC Scan
    CAPEC-308 UDP Scan
    CAPEC-309 Network Topology Mapping
    CAPEC-310 Scanning for Vulnerable Software
    CAPEC-312 Active OS Fingerprinting
    CAPEC-313 Passive OS Fingerprinting
    CAPEC-317 IP ID Sequencing Probe
    CAPEC-318 IP 'ID' Echoed Byte-Order Probe
    CAPEC-319 IP (DF) 'Don't Fragment Bit' Echoing Probe
    CAPEC-320 TCP Timestamp Probe
    CAPEC-321 TCP Sequence Number Probe
    CAPEC-322 TCP (ISN) Greatest Common Divisor Probe
    CAPEC-323 TCP (ISN) Counter Rate Probe
    CAPEC-324 TCP (ISN) Sequence Predictability Probe
    CAPEC-325 TCP Congestion Control Flag (ECN) Probe
    CAPEC-326 TCP Initial Window Size Probe
    CAPEC-327 TCP Options Probe
    CAPEC-328 TCP 'RST' Flag Checksum Probe
    CAPEC-329 ICMP Error Message Quoting Probe
    CAPEC-330 ICMP Error Message Echoing Integrity Probe
    CAPEC-384 Application API Message Manipulation via Man-in-the-Middle
    CAPEC-385 Transaction or Event Tampering via Application API Manipulation
    CAPEC-386 Application API Navigation Remapping
    CAPEC-387 Navigation Remapping To Propagate Malicious Content
    CAPEC-388 Application API Button Hijacking
    CAPEC-441 Malicious Logic Insertion
    CAPEC-472 Browser Fingerprinting
    CAPEC-478 Modification of Windows Service Configuration
    CAPEC-479 Malicious Root Certificate
    CAPEC-497 File Discovery
    CAPEC-502 Intent Spoof
    CAPEC-503 WebView Exposure
    CAPEC-508 Shoulder Surfing
    CAPEC-510 SaaS User Request Forgery
    CAPEC-536 Data Injected During Configuration
    CAPEC-546 Incomplete Data Deletion in a Multi-Tenant Environment
    CAPEC-550 Install New Service
    CAPEC-551 Modify Existing Service
    CAPEC-552 Install Rootkit
    CAPEC-556 Replace File Extension Handlers
    CAPEC-558 Replace Trusted Executable
    CAPEC-562 Modify Shared File
    CAPEC-563 Add Malicious File to Shared Webroot
    CAPEC-564 Run Software at Logon
    CAPEC-573 Process Footprinting
    CAPEC-574 Services Footprinting
    CAPEC-575 Account Footprinting
    CAPEC-576 Group Permission Footprinting
    CAPEC-577 Owner Footprinting
    CAPEC-578 Disable Security Software
    CAPEC-59 Session Credential Falsification through Prediction
    CAPEC-60 Reusing Session IDs (aka Session Replay)
    CAPEC-616 Establish Rogue Location
    CAPEC-643 Identify Shared Files/Directories on System
    CAPEC-646 Peripheral Footprinting
    CAPEC-651 Eavesdropping
    CAPEC-75 Manipulating Writeable Configuration Files
    CAPEC-76 Manipulating Web Input to File System Calls
    CAPEC-79 Using Slashes in Alternate Encoding
    CAPEC-89 Pharming

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High