Common Vulnerabilities and Exposures (CVE)

An attacker targets a system that uses JavaScript Object Notation (JSON) as a transport mechanism between the client and the server (common in Web 2.0 systems using AJAX) to steal possibly confidential information transmitted from the server back to the client inside the JSON object by taking advantage of the loophole in the browser's Same Origin Policy that does not prohibit JavaScript from one website to be included and executed in the context of another website.

Typical severity: High

Prerequisites: JSON is used as a transport mechanism between the client and the server The target server cannot differentiate real requests from forged requests The JSON object returned from the server can be accessed by the attackers' malicious code via a script tag

Solutions: Ensure that server side code can differentiate between legitimate requests and forged requests. The solution is similar to protection against Cross Site Request Forger (CSRF), which is to use a hard to guess random nonce (that is unique to the victim's session with the server) that the attacker has no way of knowing (at least in the absence of other weaknesses). Each request from the client to the server should contain this nonce and the server should reject all requests that do not contain the nonce. On the client side, the system's design could make it difficult to get access to the JSON object content via the script tag. Since the JSON object is never assigned locally to a variable, it cannot be readily modified by the attacker before being used by a script tag. For instance, if while(1) was added to the beginning of the JavaScript returned by the server, trying to access it with a script tag would result in an infinite loop. On the other hand, legitimate client side code can remove the while(1) statement after which the JavaScript can be evaluated. A similar result can be achieved by surrounding the returned JavaScript with comment tags, or using other similar techniques (e.g. wrapping the JavaScript with HTML tags). Make the URLs in the system used to retrieve JSON objects unpredictable and unique for each user session. Ensure that to the extent possible, no sensitive data is passed from the server to the client via JSON objects. JavaScript was never intended to play that role, hence the same origin policy does not adequate address this scenario.

An attacker exploits the functionality of cache technologies to cause specific data to be cached that aids the attackers' objectives. This describes any attack whereby an attacker places incorrect or harmful material in cache. The targeted cache can be an application's cache (e.g. a web browser cache) or a public cache (e.g. a DNS or ARP cache). Until the cache is refreshed, most applications or clients will treat the corrupted cache value as valid. This can lead to a wide range of exploits including redirecting web browsers towards sites that install malware and repeatedly incorrect calculations based on the incorrect value.

Typical severity: High

Prerequisites: The attacker must be able to modify the value stored in a cache to match a desired value. The targeted application must not be able to detect the illicit modification of the cache and must trust the cache value in its calculations.

Solutions: Configuration: Disable client side caching. Implementation: Listens for query replies on a network, and sends a notification via email when an entry changes.

A domain name server translates a domain name (such as www.example.com) into an IP address that Internet hosts use to contact Internet resources. An adversary modifies a public DNS cache to cause certain names to resolve to incorrect addresses that the adversary specifies. The result is that client applications that rely upon the targeted cache for domain name resolution will be directed not to the actual address of the specified domain name but to some other address. Adversaries can use this to herd clients to sites that install malware on the victim's computer or to masquerade as part of a Pharming attack.

Typical severity: High

Prerequisites: A DNS cache must be vulnerable to some attack that allows the adversary to replace addresses in its lookup table.Client applications must trust the corrupted cashed values and utilize them for their domain name resolutions.

Solutions: Configuration: Make sure your DNS servers have been updated to the latest versions Configuration: UNIX services like rlogin, rsh/rcp, xhost, and nfs are all susceptible to wrong information being held in a cache. Care should be taken with these services so they do not rely upon DNS caches that have been exposed to the Internet. Configuration: Disable client side DNS caching.

Some APIs support scripting instructions as arguments. Methods that take scripted instructions (or references to scripted instructions) can be very flexible and powerful. However, if an attacker can specify the script that serves as input to these methods they can gain access to a great deal of functionality. For example, HTML pages support <script> tags that allow scripting languages to be embedded in the page and then interpreted by the receiving web browser. If the content provider is malicious, these scripts can compromise the client application. Some applications may even execute the scripts under their own identity (rather than the identity of the user providing the script) which can allow attackers to perform activities that would otherwise be denied to them.

Typical severity: Medium

Prerequisites: The target application must include the use of APIs that execute scripts. The target application must allow the attacker to provide some or all of the arguments to one of these script interpretation methods and must fail to adequately filter these arguments for dangerous or unwanted script commands.

Solutions:

An adversary guesses, obtains, or "rides" a trusted identifier (e.g. session ID, resource ID, cookie, etc.) to perform authorized actions under the guise of an authenticated user or service.

Typical severity: High

Prerequisites: Server software must rely on weak identifier proof and/or verification schemes. Identifiers must have long lifetimes and potential for reusability. Server software must allow concurrent sessions to exist.

Solutions: Design: utilize strong federated identity such as SAML to encrypt and sign identity tokens in transit. Implementation: Use industry standards session key generation mechanisms that utilize high amount of entropy to generate the session key. Many standard web and application servers will perform this task on your behalf. Implementation: If the identifier is used for authentication, such as in the so-called single sign on use cases, then ensure that it is protected at the same level of assurance as authentication tokens. Implementation: If the web or application server supports it, then encrypting and/or signing the identifier (such as cookie) can protect the ID if intercepted. Design: Use strong session identifiers that are protected in transit and at rest. Implementation: Utilize a session timeout for all sessions, for example 20 minutes. If the user does not explicitly logout, the server terminates their session after this period of inactivity. If the user logs back in then a new session key is generated. Implementation: Verify authenticity of all identifiers at runtime.

An attacker manipulates either egress or ingress data from a client within an application framework in order to change the content of messages. Performing this attack can allow the attacker to gain unauthorized privileges within the application, or conduct attacks such as phishing, deceptive strategies to spread malware, or traditional web-application attacks. The techniques require use of specialized software that allow the attacker to perform adversary-in-the-middle (CAPEC-94) communications between the web browser and the remote system. Despite the use of AiTH software, the attack is actually directed at the server, as the client is one node in a series of content brokers that pass information along to the application framework. Additionally, it is not true "Adversary-in-the-Middle" attack at the network layer, but an application-layer attack the root cause of which is the master applications trust in the integrity of code supplied by the client.

Typical severity: Low

Prerequisites: Targeted software is utilizing application framework APIs

Solutions:

An attacker hosts or joins an event or transaction within an application framework in order to change the content of messages or items that are being exchanged. Performing this attack allows the attacker to manipulate content in such a way as to produce messages or content that look authentic but may contain deceptive links, substitute one item or another, spoof an existing item and conduct a false exchange, or otherwise change the amounts or identity of what is being exchanged. The techniques require use of specialized software that allow the attacker to man-in-the-middle communications between the web browser and the remote system in order to change the content of various application elements. Often, items exchanged in game can be monetized via sales for coin, virtual dollars, etc. The purpose of the attack is for the attack to scam the victim by trapping the data packets involved the exchange and altering the integrity of the transfer process.

Typical severity: Medium

Prerequisites: Targeted software is utilizing application framework APIs

Solutions:

An attacker manipulates either egress or ingress data from a client within an application framework in order to change the destination and/or content of links/buttons displayed to a user within API messages. Performing this attack allows the attacker to manipulate content in such a way as to produce messages or content that looks authentic but contains links/buttons that point to an attacker controlled destination. Some applications make navigation remapping more difficult to detect because the actual HREF values of images, profile elements, and links/buttons are masked. One example would be to place an image in a user's photo gallery that when clicked upon redirected the user to an off-site location. Also, traditional web vulnerabilities (such as CSRF) can be constructed with remapped buttons or links. In some cases navigation remapping can be used for Phishing attacks or even means to artificially boost the page view, user site reputation, or click-fraud.

Typical severity: Medium

Prerequisites: Targeted software is utilizing application framework APIs

Solutions:

An adversary manipulates either egress or ingress data from a client within an application framework in order to change the content of messages and thereby circumvent the expected application logic.

Typical severity: Medium

Prerequisites: Targeted software is utilizing application framework APIs

Solutions:

An attacker manipulates either egress or ingress data from a client within an application framework in order to change the destination and/or content of buttons displayed to a user within API messages. Performing this attack allows the attacker to manipulate content in such a way as to produce messages or content that looks authentic but contains buttons that point to an attacker controlled destination.

Typical severity: Medium

Prerequisites: Targeted software is utilizing application framework APIs

Solutions:

An adversary, through a previously installed malicious application, performs malicious actions against a third-party Software as a Service (SaaS) application (also known as a cloud based application) by leveraging the persistent and implicit trust placed on a trusted user's session. This attack is executed after a trusted user is authenticated into a cloud service, "piggy-backing" on the authenticated session, and exploiting the fact that the cloud service believes it is only interacting with the trusted user. If successful, the actions embedded in the malicious application will be processed and accepted by the targeted SaaS application and executed at the trusted user's privilege level.

Typical severity: Medium

Prerequisites: An adversary must be able install a purpose built malicious application onto the trusted user's system and convince the user to execute it while authenticated to the SaaS application.

Solutions: To limit one's exposure to this type of attack, tunnel communications through a secure proxy service. Detection of this type of attack can be done through heuristic analysis of behavioral anomalies (a la credit card fraud detection) which can be used to identify inhuman behavioral patterns. (e.g., spidering)

This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking.

Typical severity: High

Prerequisites: The target host uses session IDs to keep track of the users. Session IDs are used to control access to resources. The session IDs used by the target host are predictable. For example, the session IDs are generated using predictable information (e.g., time).

Solutions: Use a strong source of randomness to generate a session ID. Use adequate length session IDs Do not use information available to the user in order to generate session ID (e.g., time). Ideas for creating random numbers are offered by Eastlake [RFC1750] Encrypt the session ID if you expose it to the user. For instance session ID can be stored in a cookie in encrypted format.

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.

Typical severity: High

Prerequisites: The target host uses session IDs to keep track of the users. Session IDs are used to control access to resources. The session IDs used by the target host are not well protected from session theft.

Solutions: Always invalidate a session ID after the user logout. Setup a session time out for the session IDs. Protect the communication between the client and server. For instance it is best practice to use SSL to mitigate adversary in the middle attacks (CAPEC-94). Do not code send session ID with GET method, otherwise the session ID will be copied to the URL. In general avoid writing session IDs in the URLs. URLs can get logged in log files, which are vulnerable to an attacker. Encrypt the session data associated with the session ID. Use multifactor authentication.

Generally these are manually edited files that are not in the preview of the system administrators, any ability on the attackers' behalf to modify these files, for example in a CVS repository, gives unauthorized access directly to the application, the same as authorized users.

Typical severity: Very High

Prerequisites: Configuration files must be modifiable by the attacker

Solutions: Design: Enforce principle of least privilege Design: Backup copies of all configuration files Implementation: Integrity monitoring for configuration files Implementation: Enforce audit logging on code and configuration promotion procedures. Implementation: Load configuration from separate process and memory space, for example a separate physical device like a CD

An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.

Typical severity: Very High

Prerequisites: Program must allow for user controlled variables to be applied directly to the filesystem

Solutions: Design: Enforce principle of least privilege. Design: Ensure all input is validated, and does not contain file system commands Design: Run server interfaces with a non-root account and/or utilize chroot jails or other configuration techniques to constrain privileges even if attacker gains some limited access to commands. Design: For interactive user applications, consider if direct file system interface is necessary, instead consider having the application proxy communication. Implementation: Perform testing such as pen-testing and vulnerability scanning to identify directories, programs, and interfaces that grant direct access to executables.

A pharming attack occurs when the victim is fooled into entering sensitive data into supposedly trusted locations, such as an online bank site or a trading platform. An attacker can impersonate these supposedly trusted sites and have the victim be directed to their site rather than the originally intended one. Pharming does not require script injection or clicking on malicious links for the attack to succeed.

Typical severity: Very High

Prerequisites: Vulnerable DNS software or improperly protected hosts file or router that can be poisoned A website that handles sensitive information but does not use a secure connection and a certificate that is valid is also prone to pharming

Solutions: All sensitive information must be handled over a secure connection. Known vulnerabilities in DNS or router software or in operating systems must be patched as soon as a fix has been released and tested. End users must ensure that they provide sensitive information only to websites that they trust, over a secure connection with a valid certificate issued by a well-known certificate authority.