Base · Medium

CWE-89: Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could mod...

CWE-89 · Base Level ·15 CVEs ·10 Mitigations

Description

The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.

SQL Injection Explained

Read our in-depth guide on exploiting and mitigating this weakness

Potential Impact

Confidentiality, Integrity, Availability

Execute Unauthorized Code or Commands

Confidentiality

Read Application Data

Authentication

Gain Privileges or Assume Identity, Bypass Protection Mechanism

Access Control

Bypass Protection Mechanism

Integrity

Modify Application Data

Demonstrative Examples

The following code dynamically constructs and executes a SQL query that searches for items matching a specified name. The query restricts the items displayed to those where owner matches the user name of the currently-authenticated user.
Bad
...string userName = ctx.getAuthenticatedUserName();string query = "SELECT * FROM items WHERE owner = '" + userName + "' AND itemname = '" + ItemName.Text + "'";sda = new SqlDataAdapter(query, conn);DataTable dt = new DataTable();sda.Fill(dt);...
The query that this code intends to execute follows:
Informative
SELECT * FROM items WHERE owner = <userName> AND itemname = <itemName>;
However, because the query is constructed dynamically by concatenating a constant base query string and a user input string, the query only behaves correctly if itemName does not contain a single-quote character. If an attacker with the user name wiley enters the string:
Attack
name' OR 'a'='a
for itemName, then the query becomes the following:
Attack
SELECT * FROM items WHERE owner = 'wiley' AND itemname = 'name' OR 'a'='a';
The addition of the:
Attack
OR 'a'='a
condition causes the WHERE clause to always evaluate to true, so the query becomes logically equivalent to the much simpler query:
Attack
SELECT * FROM items;
This simplification of the query allows the attacker to bypass the requirement that the query only return items owned by the authenticated user; the query now returns all entries stored in the items table, regardless of their specified owner.
This example examines the effects of a different malicious value passed to the query constructed and executed in the previous example.
If an attacker with the user name wiley enters the string:
Attack
name'; DELETE FROM items; --
for itemName, then the query becomes the following two queries:
Attack
SELECT * FROM items WHERE owner = 'wiley' AND itemname = 'name';DELETE FROM items;
                     --'
Many database servers, including Microsoft(R) SQL Server 2000, allow multiple SQL statements separated by semicolons to be executed at once. While this attack string results in an error on Oracle and other database servers that do not allow the batch-execution of statements separated by semicolons, on databases that do allow batch execution, this type of attack allows the attacker to execute arbitrary commands against the database.
Notice the trailing pair of hyphens (--), which specifies to most database servers that the remainder of the statement is to be treated as a comment and not executed. In this case the comment character serves to remove the trailing single-quote left over from the modified query. On a database where comments are not allowed to be used in this way, the general attack could still be made effective using a trick similar to the one shown in the previous example.
If an attacker enters the string
Attack
name'; DELETE FROM items; SELECT * FROM items WHERE 'a'='a
Then the following three valid statements will be created:
Attack
SELECT * FROM items WHERE owner = 'wiley' AND itemname = 'name';DELETE FROM items;SELECT * FROM items WHERE 'a'='a';
One traditional approach to preventing SQL injection attacks is to handle them as an input validation problem and either accept only characters from an allowlist of safe values or identify and escape a denylist of potentially malicious values. Allowlists can be a very effective means of enforcing strict input validation rules, but parameterized SQL statements require less maintenance and can offer more guarantees with respect to security. As is almost always the case, denylisting is riddled with loopholes that make it ineffective at preventing SQL injection attacks. For example, attackers can:
Manually escaping characters in input to SQL queries can help, but it will not make your application secure from SQL injection attacks.
Another solution commonly proposed for dealing with SQL injection attacks is to use stored procedures. Although stored procedures prevent some types of SQL injection attacks, they do not protect against many others. For example, the following PL/SQL procedure is vulnerable to the same SQL injection attack shown in the first example.
Bad
procedure get_item ( itm_cv IN OUT ItmCurTyp, usr in varchar2, itm in varchar2)is open itm_cv for' SELECT * FROM items WHERE ' || 'owner = '|| usr || ' AND itemname = ' || itm || ';end get_item;
Stored procedures typically help prevent SQL injection attacks by limiting the types of statements that can be passed to their parameters. However, there are many ways around the limitations and many interesting statements that can still be passed to stored procedures. Again, stored procedures can prevent some exploits, but they will not make your application secure against SQL injection attacks.
MS SQL has a built in function that enables shell command execution. An SQL injection in such a context could be disastrous. For example, a query of the form:
Bad
SELECT ITEM,PRICE FROM PRODUCT WHERE ITEM_CATEGORY='$user_input' ORDER BY PRICE
Where $user_input is taken from an untrusted source.
If the user provides the string:
Attack
'; exec master..xp_cmdshell 'dir' --
The query will take the following form:
Attack
SELECT ITEM,PRICE FROM PRODUCT WHERE ITEM_CATEGORY=''; exec master..xp_cmdshell 'dir' --' ORDER BY PRICE
Now, this query can be broken down into:
As can be seen, the malicious input changes the semantics of the query into a query, a shell command execution and a comment.

Mitigations & Prevention

Architecture and Design

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482]. For example, consider using persistence layers such as Hibernate or Enterprise Java Beans, which can provide significant protection against SQL injection if used properly.

Architecture and Design

If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated. Process SQL queries using prepared statements, parameterized queries, or stored procedures. These features should accept parameters or variables and support strong typi

Architecture and DesignOperation

Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations. Specifically, follow the princ

Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Implementation

While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in qu

Implementation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across relat

Architecture and Design

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

Implementation

Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success. If

Operation Moderate

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481.

OperationImplementation

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

Detection Methods

  • Automated Static Analysis — This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives. Automated static analysis might not be able to recognize when proper input validation is b
  • Automated Dynamic Analysis Moderate — This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash
  • Manual Analysis — Manual analysis can be useful for finding this weakness, but it might not achieve desired code coverage within limited time constraints. This becomes difficult for weaknesses that must be considered for all inputs, since the attack surface can be too large.
  • Automated Static Analysis - Binary or Bytecode High — According to SOAR [REF-1479], the following detection techniques may be useful:
  • Dynamic Analysis with Automated Results Interpretation High — According to SOAR [REF-1479], the following detection techniques may be useful:
  • Dynamic Analysis with Manual Results Interpretation SOAR Partial — According to SOAR [REF-1479], the following detection techniques may be useful:

Real-World CVE Examples

CVE IDDescription
CVE-2024-6847SQL injection in AI chatbot via a conversation message
CVE-2025-26794SQL injection in e-mail agent through SQLite integration
CVE-2023-32530SQL injection in security product dashboard using crafted certificate fields
CVE-2021-42258SQL injection in time and billing software, as exploited in the wild per CISA KEV.
CVE-2021-27101SQL injection in file-transfer system via a crafted Host header, as exploited in the wild per CISA KEV.
CVE-2020-12271SQL injection in firewall product's admin interface or user portal, as exploited in the wild per CISA KEV.
CVE-2019-3792An automation system written in Go contains an API that is vulnerable to SQL injection allowing the attacker to read privileged data.
CVE-2004-0366chain: SQL injection in library intended for database authentication allows SQL injection and authentication bypass.
CVE-2008-2790SQL injection through an ID that was supposed to be numeric.
CVE-2008-2223SQL injection through an ID that was supposed to be numeric.
CVE-2007-6602SQL injection via user name.
CVE-2008-5817SQL injection via user name or password fields.
CVE-2003-0377SQL injection in security product, using a crafted group name.
CVE-2008-2380SQL injection in authentication library.
CVE-2017-11508SQL injection in vulnerability management and reporting tool, using a crafted password.

Taxonomy Mappings

  • PLOVER: — SQL injection
  • 7 Pernicious Kingdoms: — SQL Injection
  • CLASP: — SQL injection
  • OWASP Top Ten 2007: A2 — Injection Flaws
  • OWASP Top Ten 2004: A1 — Unvalidated Input
  • OWASP Top Ten 2004: A6 — Injection Flaws
  • WASC: 19 — SQL Injection
  • Software Fault Patterns: SFP24 — Tainted input to command
  • OMG ASCSM: ASCSM-CWE-89 —
  • SEI CERT Oracle Coding Standard for Java: IDS00-J — Prevent SQL injection

Frequently Asked Questions

What is CWE-89?

CWE-89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could mod...

How can CWE-89 be exploited?

Attackers can exploit CWE-89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')) to execute unauthorized code or commands. This weakness is typically introduced during the Implementation, Implementation phase of software development.

How do I prevent CWE-89?

Key mitigations include: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482]. For example, consider using

What is the severity of CWE-89?

CWE-89 is classified as a Base-level weakness (Medium abstraction). It has been observed in 15 real-world CVEs.