CWE-77
Improper Neutralization of Special Elements used in a Command ('Command Injection')
HIGH
Draft
2006-07-19 00:00 +00:00
2024-11-19 00:00 +00:00
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Improper Neutralization of Special Elements used in a Command ('Command Injection')
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
Extended Description
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.
Informations
Modes Of Introduction
Implementation :Command injection vulnerabilities typically occur when:
- Data enters the application from an untrusted source.
- The data is part of a string that is executed as a command by the application.
Implementation : REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Applicable Platforms
Language
Class: Not Language-Specific (Undetermined)Technologies
Name: AI/ML (Undetermined)Common Consequences
| 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. This gives an attacker a privilege or capability that they would not otherwise have. |
Observed Examples
| Reference | Description |
|---|---|
| injection of sed script syntax ("sed injection") | |
| API service using a large generative AI model allows direct prompt injection to leak hard-coded system prompts or execute other prompts. | |
| anti-spam product allows injection of SNMP commands into confiuration file | |
| image program allows injection of commands in "Magick Vector Graphics (MVG)" language. | |
| 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 (CWE-88), 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") |
Potential Mitigations
Phases : Architecture and DesignIf at all possible, use library calls rather than external processes to recreate the desired functionality.
Phases : Implementation
If possible, ensure that all external commands called from the program are statically created.
Phases : 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 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.
Phases : Operation
Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
Phases : System Configuration
Assign permissions that prevent the user from accessing/opening privileged files.
Detection Methods
Automated Static Analysis
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)Effectiveness : High
Vulnerability Mapping Notes
Rationale : CWE-77 is often misused when OS command injection (CWE-78) was intended instead [REF-1287].Comments : Ensure that the analysis focuses on the root-cause error that allows the execution of commands, as there are many weaknesses that can lead to this consequence. See Terminology Notes. If the weakness involves a command language besides OS shell invocation, then CWE-77 could be used.
Related Attack Patterns
| 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. |
Notes
The "command injection" phrase carries different meanings, either as an attack or as a technical impact. The most common usage of "command injection" refers to the more-accurate OS command injection (CWE-78), but there are many command languages.
In vulnerability-focused analysis, the phrase may refer to any situation in which the adversary can execute commands of their own choosing, i.e., the focus is on the risk and/or technical impact of exploitation. Many proof-of-concept exploits focus on the ability to execute commands and may emphasize "command injection." However, there are dozens of weaknesses that can allow execution of commands. That is, the ability to execute commands could be resultant from another weakness.
To some, "command injection" can include cases in which the functionality intentionally allows the user to specify an entire command, which is then executed. In this case, the root cause weakness might be related to missing or incorrect authorization, since an adversary should not be able to specify arbitrary commands, but some users or admins are allowed.
CWE-77 and its descendants are specifically focused on behaviors in which the product is intentionally building a command to execute, and the adversary can inject separators into the command or otherwise change the command being executed.
Command injection is a common problem with wrapper programs.
References
REF-6
Seven Pernicious Kingdoms: A Taxonomy of Software Security ErrorsKatrina Tsipenyuk, Brian Chess, Gary McGraw.
https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
REF-140
Exploiting Software: How to Break CodeGreg Hoglund, Gary McGraw.
https://www.amazon.com/Exploiting-Software-How-Break-Code/dp/0201786958
REF-44
24 Deadly Sins of Software SecurityMichael Howard, David LeBlanc, John Viega.
REF-1287
Supplemental Details - 2022 CWE Top 25MITRE.
https://cwe.mitre.org/top25/archive/2022/2022_cwe_top25_supplemental.html#problematicMappingDetails
Submission
| Name | Organization | Date | Date Release | Version |
|---|---|---|---|---|
| 7 Pernicious Kingdoms | Draft 3 |
Modifications
| 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 | |
| CWE Content Team | MITRE | updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Diagram, Mapping_Notes, Modes_of_Introduction, Observed_Examples, Other_Notes, Terminology_Notes | |
| CWE Content Team | MITRE | updated Demonstrative_Examples, Relationships |
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