Home > CAPEC List > CAPEC-66: SQL Injection (Version 2.11)  

CAPEC-66: SQL Injection

SQL Injection
Definition in a New Window Definition in a New Window
Attack Pattern ID: 66
Abstraction: Standard
Status: Draft
Completeness: Complete
Presentation Filter:
+ Summary

This attack exploits target software that constructs SQL statements based on user input. An attacker crafts input strings so that when the target software constructs SQL statements based on the input, the resulting SQL statement performs actions other than those the application intended.

SQL Injection results from failure of the application to appropriately validate input. When specially crafted user-controlled input consisting of SQL syntax is used without proper validation as part of SQL queries, it is possible to glean information from the database in ways not envisaged during application design. Depending upon the database and the design of the application, it may also be possible to leverage injection to have the database execute system-related commands of the attackers' choice. SQL Injection enables an attacker to talk directly to the database, thus bypassing the application completely. Successful injection can cause information disclosure as well as ability to add or modify data in the database. In order to successfully inject SQL and retrieve information from a database, an attacker:

+ Attack Steps
  1. Survey application: The attacker first takes an inventory of the functionality exposed by the application.

    Spider web sites for all available links

    Sniff network communications with application using a utility such as WireShark.

  1. Determine user-controllable input susceptible to injection: Determine the user-controllable input susceptible to injection. For each user-controllable input that the attacker suspects is vulnerable to SQL injection, attempt to inject characters that have special meaning in SQL (such as a single quote character, a double quote character, two hyphens, a parenthesis, etc.). The goal is to create a SQL query with an invalid syntax.

    Use web browser to inject input through text fields or through HTTP GET parameters.

    Use a web application debugging tool such as Tamper Data, TamperIE, WebScarab,etc. to modify HTTP POST parameters, hidden fields, non-freeform fields, etc.

    Use network-level packet injection tools such as netcat to inject input

    Use modified client (modified by reverse engineering) to inject input.

  2. Experiment and try to exploit SQL Injection vulnerability: After determining that a given input is vulnerable to SQL Injection, hypothesize what the underlying query looks like. Iteratively try to add logic to the query to extract information from the database, or to modify or delete information in the database.

    Use public resources such as "SQL Injection Cheat Sheet" at http://ferruh.mavituna.com/makale/sql-injection-cheatsheet/, and try different approaches for adding logic to SQL queries.

    Add logic to query, and use detailed error messages from the server to debug the query. For example, if adding a single quote to a query causes an error message, try : "' OR 1=1; --", or something else that would syntactically complete a hypothesized query. Iteratively refine the query.

    Use "Blind SQL Injection" techniques to extract information about the database schema.

    If a denial of service attack is the goal, try stacking queries. This does not work on all platforms (most notably, it does not work on Oracle or MySQL). Examples of inputs to try include: "'; DROP TABLE SYSOBJECTS; --" and "'); DROP TABLE SYSOBJECTS; --". These particular queries will likely not work because the SYSOBJECTS table is generally protected.

+ Attack Prerequisites
  • SQL queries used by the application to store, retrieve or modify data.

  • User-controllable input that is not properly validated by the application as part of SQL queries.

+ Typical Severity


+ Typical Likelihood of Exploit

Likelihood: Very High

+ Methods of Attack
  • Injection
+ Examples-Instances


With PHP-Nuke versions 7.9 and earlier, an attacker can successfully access and modify data, including sensitive contents such as usernames and password hashes, and compromise the application through SQL Injection. The protection mechanism against SQL Injection employs a blacklist approach to input validation. However, because of improper blacklisting, it is possible to inject content such as "foo'/**/UNION" or "foo UNION/**/" to bypass validation and glean sensitive information from the database.

Related Vulnerabilities

+ Attacker Skills or Knowledge Required

Skill or Knowledge Level: Low

It is fairly simple for someone with basic SQL knowledge to perform SQL injection, in general. In certain instances, however, specific knowledge of the database employed may be required.

+ Resources Required

None: No specialized resources are required to execute this type of attack.

+ Probing Techniques

The attacker tries to inject characters that can cause a SQL error, such as single-quote (') or keywords such as "UNION" and "OR". If the injection of such characters into the input causes a SQL error and the resulting error is displayed unfiltered, the attacker can begin to determine the nature of input validation and structure of SQL queries. A typical error resulting from such injection would look like:

"You have an error in your SQL Syntax. Check your manual for the right syntax to use near
') FROM db_users.user_table"

With available design documentation and code, the attacker can determine whether all user-controllable inputs are being validated or not, and also the structure of SQL queries that such inputs feed into.

+ Indicators-Warnings of Attack

Too many false or invalid queries to the database, especially those caused by malformed input.

+ Solutions and Mitigations

Strong input validation - All user-controllable input must be validated and filtered for illegal characters as well as SQL content. Keywords such as UNION, SELECT or INSERT must be filtered in addition to characters such as a single-quote(') or SQL-comments (--) based on the context in which they appear.

Use of parameterized queries or stored procedures - Parameterization causes the input to be restricted to certain domains, such as strings or integers, and any input outside such domains is considered invalid and the query fails. Note that SQL Injection is possible even in the presence of stored procedures if the eventual query is constructed dynamically.

Use of custom error pages - Attackers can glean information about the nature of queries from descriptive error messages. Input validation must be coupled with customized error pages that inform about an error without disclosing information about the database or application.

+ Attack Motivation-Consequences
ScopeTechnical ImpactNote
Modify application data
Read application data
Execute unauthorized code or commands
Run Arbitrary Code
Gain privileges / assume identity
+ Injection Vector

User-controllable input used as part of non-parameterized SQL queries: This may include input fields on web forms, data in user-accessible files or even command-line parameters.

+ Payload

SQL statements intended to reveal information or run malicious code

+ Activation Zone

Back-end database

+ Payload Activation Impact

When malicious SQL content is executed by the database, it can lead to arbitrary queries being executed, causing disclosure of information, unauthorized access, privilege escalation and possibly system compromise.

+ Relevant Security Requirements

Special characters in user-controllable input must be escaped before use by the application.

Only use parameterized stored procedures to query the database.

Input data must be revalidated in the parameterized stored procedures.

Custom error pages must be used to handle exceptions such that they do not reveal any information about the architecture of the application or the database.

+ Purposes
  • Penetration
  • Exploitation
+ CIA Impact
Confidentiality Impact: HighIntegrity Impact: HighAvailability Impact: High
+ Technical Context
Architectural Paradigms
+ References
[R.66.1] [REF-3] "Common Weakness Enumeration (CWE)". CWE-89 - SQL Injection. Draft. The MITRE Corporation. 2007. <http://cwe.mitre.org/data/definitions/89.html>.
[R.66.2] [REF-3] "Common Weakness Enumeration (CWE)". CWE-20 - Input Validation. Draft. The MITRE Corporation. 2007. <http://cwe.mitre.org/data/definitions/20.html>.
[R.66.3] [REF-3] "Common Weakness Enumeration (CWE)". CWE-390 - Improper Error Handling. Draft. The MITRE Corporation. 2007. <http://cwe.mitre.org/data/definitions/390.html>.
+ Content History
CAPEC Content TeamThe MITRE Corporation2014-06-23Internal_CAPEC_Team
CAPEC Content TeamThe MITRE Corporation2017-08-04Updated Resources_RequiredInternal

More information is available — Please select a different filter.
Page Last Updated or Reviewed: August 04, 2017