Command injection vulnerabilities typically occur when:
Many protocols and products have their own custom command language. While OS or shell command strings are frequently discovered and targeted, developers may not realize that these other command languages might also be vulnerable to attacks.
Command injection is a common problem with wrapper programs.
Scope | Impact | Likelihood |
---|---|---|
Integrity Confidentiality Availability | Execute Unauthorized Code or Commands Note: If a malicious user injects a character (such as a semi-colon) that delimits the end of one command and the beginning of another, it may be possible to then insert an entirely new and unrelated command that was not intended to be executed. |
Reference | Description |
---|---|
Python-based dependency management tool avoids OS command injection when generating Git commands but allows injection of optional arguments with input beginning with a dash, potentially allowing for code execution. | |
Canonical example of OS command injection. CGI program does not neutralize "|" metacharacter when invoking a phonebook program. | |
Chain: improper input validation (CWE-20) in username parameter, leading to OS command injection (CWE-78), as exploited in the wild per CISA KEV. | |
injection of sed script syntax ("sed injection") | |
injection of sed script syntax ("sed injection") | |
injection of sed script syntax ("sed injection") | |
image program allows injection of commands in "Magick Vector Graphics (MVG)" language. | |
anti-spam product allows injection of SNMP commands into confiuration file |
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 related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
CAPEC-ID | Attack Pattern Name |
---|---|
CAPEC-136 | LDAP Injection An attacker manipulates or crafts an LDAP query for the purpose of undermining the security of the target. Some applications use user input to create LDAP queries that are processed by an LDAP server. For example, a user might provide their username during authentication and the username might be inserted in an LDAP query during the authentication process. An attacker could use this input to inject additional commands into an LDAP query that could disclose sensitive information. For example, entering a * in the aforementioned query might return information about all users on the system. This attack is very similar to an SQL injection attack in that it manipulates a query to gather additional information or coerce a particular return value. |
CAPEC-15 | Command Delimiters An attack of this type exploits a programs' vulnerabilities that allows an attacker's commands to be concatenated onto a legitimate command with the intent of targeting other resources such as the file system or database. The system that uses a filter or denylist input validation, as opposed to allowlist validation is vulnerable to an attacker who predicts delimiters (or combinations of delimiters) not present in the filter or denylist. As with other injection attacks, the attacker uses the command delimiter payload as an entry point to tunnel through the application and activate additional attacks through SQL queries, shell commands, network scanning, and so on. |
CAPEC-183 | IMAP/SMTP Command Injection An adversary exploits weaknesses in input validation on web-mail servers to execute commands on the IMAP/SMTP server. Web-mail servers often sit between the Internet and the IMAP or SMTP mail server. User requests are received by the web-mail servers which then query the back-end mail server for the requested information and return this response to the user. In an IMAP/SMTP command injection attack, mail-server commands are embedded in parts of the request sent to the web-mail server. If the web-mail server fails to adequately sanitize these requests, these commands are then sent to the back-end mail server when it is queried by the web-mail server, where the commands are then executed. This attack can be especially dangerous since administrators may assume that the back-end server is protected against direct Internet access and therefore may not secure it adequately against the execution of malicious commands. |
CAPEC-248 | Command Injection An adversary looking to execute a command of their choosing, injects new items into an existing command thus modifying interpretation away from what was intended. Commands in this context are often standalone strings that are interpreted by a downstream component and cause specific responses. This type of attack is possible when untrusted values are used to build these command strings. Weaknesses in input validation or command construction can enable the attack and lead to successful exploitation. |
CAPEC-40 | Manipulating Writeable Terminal Devices This attack exploits terminal devices that allow themselves to be written to by other users. The attacker sends command strings to the target terminal device hoping that the target user will hit enter and thereby execute the malicious command with their privileges. The attacker can send the results (such as copying /etc/passwd) to a known directory and collect once the attack has succeeded. |
CAPEC-43 | Exploiting Multiple Input Interpretation Layers An attacker supplies the target software with input data that contains sequences of special characters designed to bypass input validation logic. This exploit relies on the target making multiples passes over the input data and processing a "layer" of special characters with each pass. In this manner, the attacker can disguise input that would otherwise be rejected as invalid by concealing it with layers of special/escape characters that are stripped off by subsequent processing steps. The goal is to first discover cases where the input validation layer executes before one or more parsing layers. That is, user input may go through the following logic in an application: |
CAPEC-75 | Manipulating Writeable Configuration Files 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. |
CAPEC-76 | Manipulating Web Input to File System Calls 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. |
The "command injection" phrase carries different meanings to different people. For some people, it refers to any type of attack that can allow the attacker to execute commands of their own choosing, regardless of how those commands are inserted. The command injection could thus be resultant from another weakness. This usage also includes cases in which the functionality allows the user to specify an entire command, which is then executed; within CWE, this situation might be better regarded as an authorization problem (since an attacker should not be able to specify arbitrary commands.)
Another common usage, which includes CWE-77 and its descendants, involves cases in which the attacker injects separators into the command being constructed.
Name | Organization | Date | Date Release | Version |
---|---|---|---|---|
7 Pernicious Kingdoms | Draft 3 |
Name | Organization | Date | Comment |
---|---|---|---|
Eric Dalci | Cigital | updated Time_of_Introduction | |
Veracode | Suggested OWASP Top Ten 2004 mapping | ||
CWE Content Team | MITRE | updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities | |
CWE Content Team | MITRE | updated Demonstrative_Examples, Name | |
CWE Content Team | MITRE | updated Demonstrative_Examples, Description, Name | |
CWE Content Team | MITRE | updated Common_Consequences, Description, Other_Notes, Potential_Mitigations | |
CWE Content Team | MITRE | updated Potential_Mitigations, Relationships | |
CWE Content Team | MITRE | updated Description, Name | |
CWE Content Team | MITRE | updated Demonstrative_Examples | |
CWE Content Team | MITRE | updated Common_Consequences | |
CWE Content Team | MITRE | updated Common_Consequences, Demonstrative_Examples, References, Related_Attack_Patterns, Relationships | |
CWE Content Team | MITRE | updated Potential_Mitigations | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Applicable_Platforms, Demonstrative_Examples, Description, Other_Notes, Terminology_Notes | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Demonstrative_Examples, Relationships | |
CWE Content Team | MITRE | updated Potential_Mitigations, Related_Attack_Patterns, Relationships | |
CWE Content Team | MITRE | updated Causal_Nature, Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships, Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Taxonomy_Mappings | |
CWE Content Team | MITRE | updated Related_Attack_Patterns, Relationships | |
CWE Content Team | MITRE | updated Potential_Mitigations, References, Relationships | |
CWE Content Team | MITRE | updated Potential_Mitigations | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Description, Observed_Examples, Relationships | |
CWE Content Team | MITRE | updated Relationships | |
CWE Content Team | MITRE | updated Observed_Examples, Relationships | |
CWE Content Team | MITRE | updated Observed_Examples, References, Terminology_Notes | |
CWE Content Team | MITRE | updated Description, Potential_Mitigations | |
CWE Content Team | MITRE | updated Detection_Factors, Relationships, Time_of_Introduction | |
CWE Content Team | MITRE | updated Mapping_Notes, Relationships |