CVE-2017-7828 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur when flushing and resizing layout because the "PressShell" object has been freed while still in use. This results in a potentially exploitable crash during these operations. This vulnerability affects Firefox < 57, Firefox ESR < 52.5, and Thunderbird < 52.5.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2017-7828 represents a critical use-after-free flaw in Mozilla Firefox and Thunderbird applications that stems from improper memory management during layout operations. This vulnerability specifically manifests when the PressShell object undergoes deallocation while still being referenced by active processes, creating a scenario where subsequent memory access attempts can lead to unpredictable behavior and potential code execution. The flaw exists within the browser's rendering engine and affects versions prior to Firefox 57, Firefox ESR 52.5, and Thunderbird 52.5, making it a significant concern for organizations still operating legacy software versions.
The technical nature of this vulnerability aligns with CWE-416, which defines use-after-free conditions as a common memory safety issue where a program continues to reference memory after it has been freed. In this specific case, the PressShell object serves as a critical component in Firefox's layout system responsible for managing document rendering and display operations. When the system flushes and resizes layout operations, the memory management logic fails to properly track object references, allowing the PressShell object to be destroyed while active rendering processes still depend on it. This creates a race condition where memory corruption occurs during the cleanup process, potentially leading to arbitrary code execution if an attacker can control the memory contents.
The operational impact of CVE-2017-7828 extends beyond simple application instability, as it presents a potential pathway for remote code execution in targeted attacks. Attackers could leverage this vulnerability by crafting malicious web content that triggers the specific layout operations causing the memory corruption, potentially enabling them to execute arbitrary code with the privileges of the affected browser process. The vulnerability's exploitation requires a sophisticated attack vector that involves precise control over the browser's rendering pipeline and memory allocation patterns, making it particularly dangerous in environments where users encounter untrusted web content. Security researchers have documented this issue as part of the broader ATT&CK framework under the technique of code injection, specifically targeting memory corruption vulnerabilities that allow privilege escalation.
Organizations affected by CVE-2017-7828 should prioritize immediate remediation through software updates to versions that include memory management fixes for the PressShell object. The vulnerability demonstrates the importance of proper object lifecycle management in complex browser applications and highlights the need for comprehensive memory safety testing. System administrators should implement network-based mitigations including web filtering and content sandboxing while ensuring that all endpoints receive the necessary security patches. Additionally, organizations should conduct thorough vulnerability assessments to identify any remaining legacy systems that may be vulnerable to similar memory corruption issues, as this represents a pattern of security flaws that require careful attention to memory management practices in modern web browsers.