Home > CAPEC List > CAPEC-215: Fuzzing and observing application log data/errors for application mapping (Version 3.2)  

CAPEC-215: Fuzzing and observing application log data/errors for application mapping

Attack Pattern ID: 215
Abstraction: Detailed
Status: Draft
Presentation Filter:
+ Description
An attacker sends random, malformed, or otherwise unexpected messages to a target application and observes the application's log or error messages returned. Fuzzing techniques involve sending random or malformed messages to a target and monitoring the target's response. The attacker does not initially know how a target will respond to individual messages but by attempting a large number of message variants they may find a variant that trigger's desired behavior. In this attack, the purpose of the fuzzing is to observe the application's log and error messages, although fuzzing a target can also sometimes cause the target to enter an unstable state, causing a crash. By observing logs and error messages, the attacker can learn details about the configuration of the target application and might be able to cause the target to disclose sensitive information.
+ Likelihood Of Attack


+ Typical Severity


+ Relationships

The table below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.

ChildOfStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.54Query System for Information

The table below shows the views that this attack pattern belongs to and top level categories within that view.

+ Execution Flow
  1. Probing: The attacker uses fuzzing tools to send random malformed messages to web server and observes for server's log or error message.

    The attacker uses fuzzing tools to send random malformed messages to web server and observes for server's log or error message.
  1. Modify the parameters to get the desired information from the error messages.: Attacker usually needs to modify the fuzzing parameters according to the observed error messages to get the desired sensitive information for the application. To defeat correlation, the attacker may try changing the origin IP addresses or client browser identification strings or start a new session from where he left off in obfuscating the attack.

    Modify the parameters in the fuzzing tool according to the observed error messages. Repeat with enough parameters until the application has been sufficiently mapped.
    If the application rejects the large amount of fuzzing messages from the same host machine, the attacker needs to hide the attacks by changing the IP addresses or other credentials.
+ Prerequisites
The target application must fail to sanitize incoming messages adequately before processing.
+ Skills Required
[Level: Medium]
Although fuzzing parameters is not difficult, and often possible with automated fuzzing tools, interpreting the error conditions and modifying the parameters so as to move further in the process of mapping the application requires detailed knowledge of target platform, the languages and packages used as well as software design.
+ Resources Required
Fuzzing tools, which automatically generate and send message variants, are necessary for this attack. The attacker must have sufficient access to send messages to the target. The attacker must also have the ability to observe the target application's log and/or error messages in order to collect information about the target.
+ Consequences

The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

+ Mitigations
Design: Construct a 'code book' for error messages. When using a code book, application error messages aren't generated in string or stack trace form, but are catalogued and replaced with a unique (often integer-based) value 'coding' for the error. Such a technique will require helpdesk and hosting personnel to use a 'code book' or similar mapping to decode application errors/logs in order to respond to them normally.
Design: wrap application functionality (preferably through the underlying framework) in an output encoding scheme that obscures or cleanses error messages to prevent such attacks. Such a technique is often used in conjunction with the above 'code book' suggestion.
Implementation: Obfuscate server fields of HTTP response.
Implementation: Hide inner ordering of HTTP response header.
Implementation: Customizing HTTP error codes such as 404 or 500.
Implementation: Hide HTTP response header software information filed.
Implementation: Hide cookie's software information filed.
Implementation: Obfuscate database type in Database API's error message.
+ Example Instances

The following code generates an error message that leaks the full pathname of the configuration file.

$ConfigDir = "/home/myprog/config"; $uname = GetUserInput("username"); ExitError("Bad hacker!") if ($uname !~ /^\w+$/); $file = "$ConfigDir/$uname.txt"; if (! (-e $file)) { ExitError("Error: $file does not exist"); } ...

If this code is running on a server, such as a web application, then the person making the request should not know what the full pathname of the configuration directory is. By submitting a username that does not produce a $file that exists, an attacker could get this pathname. It could then be used to exploit path traversal or symbolic link following problems that may exist elsewhere in the application.

+ Content History
Submission DateSubmitterOrganization
2014-06-23CAPEC Content TeamThe MITRE Corporation
Modification DateModifierOrganization
2018-07-31CAPEC Content TeamThe MITRE Corporation
Updated References
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Page Last Updated or Reviewed: September 30, 2019