CVE-2021-40539

Passing Local Filenames to Functions That Expect a URL (CAPEC-48)

This attack relies on client side code to access local files and resources instead of URLs. When the client browser is expecting a URL string, but instead receives a request for a local file, that execution is likely to occur in the browser process space with the browser's authority to local files. The attacker can send the results of this request to the local files out to a site that they control. This attack may be used to steal sensitive authentication data (either local or remote), or to gain system profile information to launch further attacks.

Create files with the same name as files protected with a higher classification (CAPEC-177)

An attacker exploits file location algorithms in an operating system or application by creating a file with the same name as a protected or privileged file. The attacker could manipulate the system if the attacker-created file is trusted by the operating system or an application component that attempts to load the original file. Applications often load or include external files, such as libraries or configuration files. These files should be protected against malicious manipulation. However, if the application only uses the name of the file when locating it, an attacker may be able to create a file with the same name and place it in a directory that the application will search before the directory with the legitimate file is searched. Because the attackers' file is discovered first, it would be used by the target application. This attack can be extremely destructive if the referenced file is executable and/or is granted special privileges based solely on having a particular name.

Redirect Access to Libraries (CAPEC-159)

An adversary exploits a weakness in the way an application searches for external libraries to manipulate the execution flow to point to an adversary supplied library or code base. This pattern of attack allows the adversary to compromise the application or server via the execution of unauthorized code. An application typically makes calls to functions that are a part of libraries external to the application. These libraries may be part of the operating system or they may be third party libraries. If an adversary can redirect an application's attempts to access these libraries to other libraries that the adversary supplies, the adversary will be able to force the targeted application to execute arbitrary code. This is especially dangerous if the targeted application has enhanced privileges. Access can be redirected through a number of techniques, including the use of symbolic links, search path modification, and relative path manipulation.

DLL Side-Loading (CAPEC-641)

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.

CVE.org

View more information about CVE-2021-40539 on the official MITRE CVE website.

NIST National Vulnerability Database

CVE-2021-40539 on the NIST NVD.

CISA Known Exploited Vulnerabilities

CISA KEV