CAPEC-641 Detail

An adversary places a malicious version of a Dynamic-Link Library (DLL) in the Windows Side-by-Side (WinSxS) directory to trick the operating system into loading this malicious DLL instead of a legitimate DLL. Programs specify the location of the DLLs to load via the use of WinSxS manifests or DLL redirection and if they aren't used then Windows searches in a predefined set of directories to locate the file. If the applications improperly specify a required DLL or WinSxS manifests aren't explicit about the characteristics of the DLL to be loaded, they can be vulnerable to side-loading.

Prerequisites

The target must fail to verify the integrity of the DLL before using them.

Skills Required

Trick the operating system in loading a malicious DLL instead of a legitimate DLL.

Mitigations

Prevent unknown DLLs from loading through using an allowlist policy.
Patch installed applications as soon as new updates become available.
Properly restrict the location of the software being used.
Use of sxstrace.exe on Windows as well as manual inspection of the manifests.
Require code signing and avoid using relative paths for resources.

Related Weaknesses

References

REF-501

DLL SIDE-LOADING: A Thorn in the Side of the Anti-Virus Industry
Stewart A..
https://www.fireeye.com/content/dam/fireeye-www/global/en/current-threats/pdfs/rpt-dll-sideloading.pdf

Submission

Modifications