CVE-2017-5469 in Firefox
Summary
by MITRE
Fixed potential buffer overflows in generated Firefox code due to CVE-2016-6354 issue in Flex. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2017-5469 represents a critical buffer overflow condition that emerged from the integration of Adobe Flex technology within Mozilla Firefox and Thunderbird applications. This issue stems from a fundamental flaw in how generated code handles memory allocation when processing Flex-based content, creating potential attack vectors that could be exploited by malicious actors. The vulnerability specifically manifests in applications that utilize the Flex framework for generating ActionScript code, which then executes within the browser environment. The root cause lies in improper bounds checking and memory management practices within the Flex compiler and runtime environment, particularly when handling dynamically generated code sequences.
The technical implementation of this vulnerability involves the exploitation of buffer overflow conditions that occur during the compilation and execution of Flex-generated ActionScript code. When Flex processes certain input parameters or data structures, it fails to properly validate the size of memory allocations, leading to scenarios where data can be written beyond allocated buffer boundaries. This creates opportunities for attackers to manipulate memory contents and potentially execute arbitrary code with the privileges of the affected application. The vulnerability is particularly dangerous because it operates at the intersection of multiple software components, including the Flex compiler, ActionScript runtime, and browser rendering engines, making detection and prevention challenging. According to CWE standards, this vulnerability maps to CWE-121, which specifically addresses stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios.
The operational impact of CVE-2017-5469 extends across multiple Mozilla products and versions, creating widespread exposure for organizations using affected software. Thunderbird versions prior to 52.1, Firefox Extended Support Release versions before 45.9 and 52.1, and Firefox versions before 53 are all vulnerable to this condition, affecting users who may be processing Flex-based content or encountering malicious web pages that trigger the vulnerable code paths. Attackers could leverage this vulnerability through malicious websites, email attachments, or compromised web applications that utilize Flex technology, potentially leading to complete system compromise. The vulnerability's exploitation could result in arbitrary code execution, privilege escalation, and data theft, making it particularly concerning for enterprise environments. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving code injection and privilege escalation, specifically mapping to tactics such as execution and privilege escalation within the adversary lifecycle.
Organizations should implement immediate mitigation strategies to address this vulnerability, including updating to the latest supported versions of affected software products. The recommended approach involves upgrading Thunderbird to version 52.1 or later, Firefox ESR to versions 45.9 or 52.1, and standard Firefox releases to version 53 or higher. Additionally, security administrators should consider implementing network-based controls such as web application firewalls and content filtering solutions to block access to known malicious Flex-based content. Regular security assessments should be conducted to identify and remediate any remaining instances of vulnerable software within the organization's infrastructure. The mitigation strategy should also include monitoring for exploitation attempts and implementing proper incident response procedures to address potential compromise events. Organizations utilizing older versions of these applications should prioritize migration to supported releases to ensure continued protection against this and similar vulnerabilities.