Common Weakness Enumeration

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CWE-428: Unquoted Search Path or Element

Unquoted Search Path or Element
Weakness ID: 428 (Weakness Base)Status: Draft
+ Description

Description Summary

The product uses a search path that contains an unquoted element, in which the element contains whitespace or other separators. This can cause the product to access resources in a parent path.

Extended Description

If a malicious individual has access to the file system, it is possible to elevate privileges by inserting such a file as "C:\Program.exe" to be run by a privileged program making use of WinExec.

+ Time of Introduction
  • Implementation
+ Applicable Platforms



Operating Systems

Windows 2000: (Sometimes)

Windows XP: (Sometimes)

Windows Vista: (Sometimes)

Mac OS X: (Rarely)

Platform Notes

This weakness could apply to any OS that supports spaces in filenames, especially any OS that make it easy for a user to insert spaces into filenames or folders, such as Windows. While spaces are technically supported in Unix, the practice is generally avoided. .

+ Common Consequences

Technical Impact: Execute unauthorized code or commands

+ Demonstrative Examples

Example 1

(Bad Code)
Example Languages: C and C++ 
UINT errCode = WinExec( "C:\\Program Files\\Foo\\Bar", SW_SHOW );
+ Observed Examples
Small handful of others. Program doesn't quote the "C:\Program Files\" path when calling a program to be executed - or any other path with a directory or file whose name contains a space - so attacker can put a malicious program.exe into C:.
CreateProcess() and CreateProcessAsUser() can be misused by applications to allow "program.exe" style attacks in C:
Applies to "Common Files" folder, with a malicious common.exe, instead of "Program Files"/program.exe.
+ Potential Mitigations

Phase: Implementation

Properly quote the full search path before executing a program on the system.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist 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 (i.e., do not rely on a blacklist). A blacklist 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, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory417Channel and Path Errors
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class668Exposure of Resource to Wrong Sphere
Research Concepts (primary)1000
ChildOfCategoryCategory893SFP Cluster: Path Resolution
Software Fault Pattern (SFP) Clusters (primary)888
+ Research Gaps

Under-studied, probably under-reported.

+ Functional Areas
  • Program invocation
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERUnquoted Search Path or Element
+ References
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 11, "Process Loading", Page 654.. 1st Edition. Addison Wesley. 2006.
+ Maintenance Notes

This weakness primarily involves the lack of quoting, which is not explicitly stated as a part of CWE-116. CWE-116 also describes output in light of structured messages, but the generation of a filename or search path (as in this weakness) might not be considered a structured message.

An additional complication is the relationship to control spheres. Unlike untrusted search path (CWE-426), which inherently involves control over the definition of a control sphere, this entry concerns a fixed control sphere in which some part of the sphere may be under attacker control. This is not a clean fit under CWE-668 or CWE-610, which suggests that the control sphere model needs enhancement or clarification.

+ Content History
Submission DateSubmitterOrganizationSource
Externally Mined
Modification DateModifierOrganizationSource
updated Potential_Mitigations, Time_of_Introduction
updated Relationships, Other_Notes, Taxonomy_Mappings
updated Applicable_Platforms, Description, Maintenance_Notes, Other_Notes, Potential_Mitigations, Relationships
updated Other_Notes
updated Potential_Mitigations
updated Common_Consequences
updated References, Relationships
updated Potential_Mitigations
Page Last Updated: June 23, 2014