CVE-2017-7782 in Firefox
Summary
by MITRE
An error in the "WindowsDllDetourPatcher" where a RWX ("Read/Write/Execute") 4k block is allocated but never protected, violating DEP protections. Note: This attack only affects Windows operating systems. Other operating systems are not affected. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2017-7782 represents a critical memory protection flaw within the WindowsDllDetourPatcher component that specifically targets Mozilla Firefox and Thunderbird applications. This issue stems from improper memory management practices where a 4 kilobyte memory block is allocated with read, write, and execute permissions simultaneously, creating a dangerous execution environment that bypasses fundamental operating system security mechanisms. The flaw exists in the Windows operating system environment where the patcher component fails to properly enforce Data Execution Prevention (DEP) policies, allowing malicious code to execute within memory regions that should be protected from execution.
The technical implementation of this vulnerability involves the allocation of memory pages with RWX permissions through the WindowsDllDetourPatcher functionality, which is designed to intercept and redirect function calls within Windows DLLs. When the patcher allocates these memory blocks, it creates a 4k page that simultaneously permits reading, writing, and executing operations without proper protection mechanisms. This violates the fundamental security principle that memory pages should be either readable, writable, or executable, but never all three simultaneously. The vulnerability specifically affects Firefox versions prior to 52.3 and Thunderbird versions prior to 52.3, as well as Firefox ESR versions before 52.3, making these applications susceptible to exploitation by attackers who can leverage this memory misconfiguration.
The operational impact of this vulnerability is severe and directly aligns with the ATT&CK framework's technique T1059 for command and control communication and T1068 for exploit for privilege escalation. Attackers can exploit this flaw to execute arbitrary code within the context of the affected applications, potentially leading to complete system compromise. The vulnerability creates a persistent execution environment where malicious payloads can be loaded and executed without triggering DEP protections that are designed to prevent such attacks. This represents a classic example of a memory corruption vulnerability that allows attackers to bypass modern exploit mitigation techniques, including DEP, ASLR, and stack canaries. The vulnerability is particularly dangerous because it operates at the kernel level through Windows DLL patching mechanisms, providing attackers with elevated privileges and direct access to system resources.
The root cause of this vulnerability can be categorized under CWE-119 Improper Restriction of Operations within the Memory Pool, which specifically addresses memory access violations and improper memory protection mechanisms. The flaw demonstrates poor memory management practices where the WindowsDllDetourPatcher fails to implement proper memory protection boundaries, creating an environment where executable code can be loaded into memory regions that should be protected from execution. This vulnerability affects not only the targeted applications but also demonstrates broader issues with Windows DLL patching mechanisms that could potentially be exploited in other software components. The vulnerability's impact is amplified by the fact that it affects multiple Mozilla applications simultaneously, increasing the potential attack surface and making it a high-priority target for exploit development. Organizations using affected versions of Firefox or Thunderbird should immediately implement mitigations including updating to patched versions, implementing application whitelisting, and monitoring for suspicious memory allocation patterns that could indicate exploitation attempts.