7.8 CVE-2023-38557

In applications, particularly web applications, access to functionality is mitigated by an authorization framework. This framework maps Access Control Lists (ACLs) to elements of the application's functionality; particularly URL's for web apps. In the case that the administrator failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application, or can run queries for data that they otherwise not supposed to. [Survey] The attacker surveys the target application, possibly as a valid and authenticated user [Identify Functionality] At each step, the attacker notes the resource or functionality access mechanism invoked upon performing specific actions [Iterate over access capabilities] Possibly as a valid user, the attacker then tries to access each of the noted access mechanisms directly in order to perform functions not constrained by the ACLs.

An adversary is able to exploit features of the target that should be reserved for privileged users or administrators but are exposed to use by lower or non-privileged accounts. Access to sensitive information and functionality must be controlled to ensure that only authorized users are able to access these resources.

An adversary crafts a request to a target that results in the target listing/indexing the content of a directory as output. One common method of triggering directory contents as output is to construct a request containing a path that terminates in a directory name rather than a file name since many applications are configured to provide a list of the directory's contents when such a request is received. An adversary can use this to explore the directory tree on a target as well as learn the names of files. This can often end up revealing test files, backup files, temporary files, hidden files, configuration files, user accounts, script contents, as well as naming conventions, all of which can be used by an attacker to mount additional attacks. [Directory Discovery] Use a method, either manual, scripted, or automated to discover the directories on the server by making requests for directories that may possibly exist. During this phase the adversary is less concerned with whether a directory can be accessed or indexed and more focused on simply discovering what directories do exist on the target. [Iteratively explore directory/file structures] The adversary attempts to access the discovered directories that allow access and may attempt to bypass server or application level ACLs by using manual or automated methods [Read directories or files which are not intended for public viewing.] The adversary attempts to access the discovered directories that allow access and may attempt to bypass server or application level ACLs by using manual or automated methods

An attack of this type exploits a system's configuration that allows an adversary to either directly access an executable file, for example through shell access; or in a possible worst case allows an adversary to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface. [Determine File/Directory Configuration] The adversary looks for misconfigured files or directories on a system that might give executable access to an overly broad group of users. [Upload Malicious Files] If the adversary discovers a directory that has executable permissions, they will attempt to upload a malicious file to execute. [Execute Malicious File] The adversary either executes the uploaded malicious file, or executes an existing file that has been misconfigured to allow executable access to the adversary.

An attacker exploits a weakness in the configuration of access controls and is able to bypass the intended protection that these measures guard against and thereby obtain unauthorized access to the system or network. Sensitive functionality should always be protected with access controls. However configuring all but the most trivial access control systems can be very complicated and there are many opportunities for mistakes. If an attacker can learn of incorrectly configured access security settings, they may be able to exploit this in an attack. [Survey] The attacker surveys the target application, possibly as a valid and authenticated user. [Identify weak points in access control configurations] The attacker probes the access control for functions and data identified in the Explore phase to identify potential weaknesses in how the access controls are configured. [Access the function or data bypassing the access control] The attacker executes the function or accesses the data identified in the Explore phase bypassing the access control.

The adversary extracts credentials used for code signing from a production environment and then uses these credentials to sign malicious content with the developer's key. Many developers use signing keys to sign code or hashes of code. When users or applications verify the signatures are accurate they are led to believe that the code came from the owner of the signing key and that the code has not been modified since the signature was applied. If the adversary has extracted the signing credentials then they can use those credentials to sign their own code bundles. Users or tools that verify the signatures attached to the code will likely assume the code came from the legitimate developer and install or run the code, effectively allowing the adversary to execute arbitrary code on the victim's computer. This differs from CAPEC-673, because the adversary is performing the code signing. The adversary first attempts to obtain a digital certificate in order to sign their malware or tools. This certificate could be stolen, created by the adversary, or acquired normally through a certificate authority. Based on the type of certificate obtained, the adversary will create a goal for their attack. This is either a broad or targeted attack. If an adversary was able to steal a certificate from a targeted organization, they could target this organization by pretending to have legitimate code signed by them. In other cases, the adversary would simply sign their malware and pose as legitimate software such that any user might trust it. This is the more broad approach The adversary creates their malware and signs it with the obtained digital certificate. The adversary then checks if the code that they signed is valid either through downloading from the targeted source or testing locally. Once the malware has been signed, it is then deployed to the desired location. They wait for a trusting user to run their malware, thinking that it is legitimate software. This malware could do a variety of things based on the motivation of the adversary.

An adversary gains control of a process that is assigned elevated privileges in order to execute arbitrary code with those privileges. Some processes are assigned elevated privileges on an operating system, usually through association with a particular user, group, or role. If an attacker can hijack this process, they will be able to assume its level of privilege in order to execute their own code. [Find process with elevated priveleges] The adversary probes for processes running with elevated privileges. [Find vulnerability in running process] The adversary looks for a vulnerability in the running process that would allow for arbitrary code execution with the privilege of the running process. [Execute arbitrary code] The adversary exploits the vulnerability that they have found and hijacks the running process.

This attack targets the reuse of valid session ID to spoof the target system in order to gain privileges. The attacker tries to reuse a stolen session ID used previously during a transaction to perform spoofing and session hijacking. Another name for this type of attack is Session Replay. The attacker interacts with the target host and finds that session IDs are used to authenticate users. The attacker steals a session ID from a valid user. The attacker tries to use the stolen session ID to gain access to the system with the privileges of the session ID's original owner.

The attacker induces a client to establish a session with the target software using a session identifier provided by the attacker. Once the user successfully authenticates to the target software, the attacker uses the (now privileged) session identifier in their own transactions. This attack leverages the fact that the target software either relies on client-generated session identifiers or maintains the same session identifiers after privilege elevation. [Setup the Attack] Setup a session: The attacker has to setup a trap session that provides a valid session identifier, or select an arbitrary identifier, depending on the mechanism employed by the application. A trap session is a dummy session established with the application by the attacker and is used solely for the purpose of obtaining valid session identifiers. The attacker may also be required to periodically refresh the trap session in order to obtain valid session identifiers. [Attract a Victim] Fixate the session: The attacker now needs to transfer the session identifier from the trap session to the victim by introducing the session identifier into the victim's browser. This is known as fixating the session. The session identifier can be introduced into the victim's browser by leveraging cross site scripting vulnerability, using META tags or setting HTTP response headers in a variety of ways. [Abuse the Victim's Session] Takeover the fixated session: Once the victim has achieved a higher level of privilege, possibly by logging into the application, the attacker can now take over the session using the fixated session identifier.

An attacker crafts malicious web links and distributes them (via web pages, email, etc.), typically in a targeted manner, hoping to induce users to click on the link and execute the malicious action against some third-party application. If successful, the action embedded in the malicious link will be processed and accepted by the targeted application with the users' privilege level. This type of attack leverages the persistence and implicit trust placed in user session cookies by many web applications today. In such an architecture, once the user authenticates to an application and a session cookie is created on the user's system, all following transactions for that session are authenticated using that cookie including potential actions initiated by an attacker and simply "riding" the existing session cookie. [Explore target website] The attacker first explores the target website to determine pieces of functionality that are of interest to them (e.g. money transfers). The attacker will need a legitimate user account on the target website. It would help to have two accounts. [Create a link that when clicked on, will execute the interesting functionality.] The attacker needs to create a link that will execute some interesting functionality such as transfer money, change a password, etc. [Convince user to click on link] Finally, the attacker needs to convince a user that is logged into the target website to click on a link to execute the CSRF attack.

Adversaries know that certain binaries will be regularly executed as part of normal processing. If these binaries are not protected with the appropriate file system permissions, it could be possible to replace them with malware. This malware might be executed at higher system permission levels. A variation of this pattern is to discover self-extracting installation packages that unpack binaries to directories with weak file permissions which it does not clean up appropriately. These binaries can be replaced by malware, which can then be executed.