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CWE

Execution with Unnecessary Privileges

ID: 250		Date: (C)2012-05-14 (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Class

Description

The software performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses.

Extended Description

New weaknesses can be exposed because running with extra privileges, such as root or Administrator, can disable the normal security checks being performed by the operating system or surrounding environment. Other pre-existing weaknesses can turn into security vulnerabilities if they occur while operating at raised privileges.

Privilege management functions can behave in some less-than-obvious ways, and they have different quirks on different platforms. These inconsistencies are particularly pronounced if you are transitioning from one non-root user to another. Signal handlers and spawned processes run at the privilege of the owning process, so if a process is running as root when a signal fires or a sub-process is executed, the signal handler or sub-process will operate with root privileges.

Likelihood of Exploit: Medium

Applicable Platforms
Language Class: All

Time Of Introduction

Installation
Architecture and Design
Operation

Related Attack Patterns

Common Consequences

Scope	Technical Impact	Notes
Confidentiality Integrity Availability Access_Control	Gain privileges / assume identity Execute unauthorized code or commands Read application data DoS: crash / exit / restart	An attacker will be able to gain access to any resources that are allowed by the extra privileges. Common results include executing code, disabling services, and reading restricted data.

Detection Methods

Name	Description	Effectiveness	Notes
Manual Analysis	This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.
Black Box	Use monitoring tools that examine the software's process as it interacts with the operating system and the network. This technique is useful in cases when source code is unavailable, if the software was not developed by you, or if you want to verify that the build phase did not introduce any new weaknesses. Examples include debuggers that directly attach to the running process; system-call tracing utilities such as truss (Solaris) and strace (Linux); system activity monitors such as FileMon, RegMon, Process Monitor, and other Sysinternals utilities (Windows); and sniffers and protocol analyzers that monitor network traffic. Attach the monitor to the process and perform a login. Look for library functions and system calls that indicate when privileges are being raised or dropped. Look for accesses of resources that are restricted to normal users.

Potential Mitigations

Phase	Strategy	Description
Architecture and Design Operation	Environment Hardening	Run your code using the lowest privileges that are required to accomplish the necessary tasks [R.250.2]. 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.
Architecture and Design	Separation of Privilege Identify and Reduce Attack Surface	Identify the functionality that requires additional privileges, such as access to privileged operating system resources. Wrap and centralize this functionality if possible, and isolate the privileged code as much as possible from other code [R.250.2]. Raise privileges as late as possible, and drop them as soon as possible to avoid CWE-271. Avoid weaknesses such as CWE-288 and CWE-420 by protecting all possible communication channels that could interact with the privileged code, such as a secondary socket that is only intended to be accessed by administrators.
Implementation		Perform extensive input validation for any privileged code that must be exposed to the user and reject anything that does not fit your strict requirements.
Implementation		When dropping privileges, ensure that they have been dropped successfully to avoid CWE-273. As protection mechanisms in the environment get stronger, privilege-dropping calls may fail even if it seems like they would always succeed.
Implementation		If circumstances force you to run with extra privileges, then determine the minimum access level necessary. First identify the different permissions that the software and its users will need to perform their actions, such as file read and write permissions, network socket permissions, and so forth. Then explicitly allow those actions while denying all else [R.250.2]. Perform extensive input validation and canonicalization to minimize the chances of introducing a separate vulnerability. This mitigation is much more prone to error than dropping the privileges in the first place.
Operation System Configuration	Environment Hardening	Ensure that the software runs properly under the Federal Desktop Core Configuration (FDCC) [R.250.4] or an equivalent hardening configuration guide, which many organizations use to limit the attack surface and potential risk of deployed software.

Relationships
There is a close association with CWE-653 (Insufficient Separation of Privileges). CWE-653 is about providing separate components for each privilege; CWE-250 is about ensuring that each component has the least amount of privileges possible.

Related CWE	Type	View	Chain
CWE-250 ChildOf CWE-901	Category	CWE-888

Demonstrative Examples (Details)

Observed Examples

CVE-2007-4217 : FTP client program on a certain OS runs with setuid privileges and has a buffer overflow. Most clients do not need extra privileges, so an overflow is not a vulnerability for those clients.
CVE-2008-1877 : Program runs with privileges and calls another program with the same privileges, which allows read of arbitrary files.
CVE-2007-5159 : OS incorrectly installs a program with setuid privileges, allowing users to gain privileges.
CVE-2008-4638 : Composite: application running with high privileges allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file.
CVE-2008-0162 : Program does not drop privileges before calling another program, allowing code execution.
CVE-2008-0368 : setuid root program allows creation of arbitrary files through command line argument.
CVE-2007-3931 : Installation script installs some programs as setuid when they shouldn't be.

For more examples, refer to CVE relations in the bottom box.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings

Taxynomy	Id	Name	Fit
7 Pernicious Kingdoms		Often Misused: Privilege Management
CERT Java Secure Coding	SER09-J	Minimize privileges before deserializing from a privilege context

References:

Jerome H. Saltzer Michael D. Schroeder .The Protection of Information in Computer Systems. Proceedings of the IEEE 63. Published on September, 1975.
Sean Barnum Michael Gegick .Least Privilege. Published on 2005-09-14.
M. Howard D. LeBlanc .Writing Secure Code 2nd Edition. Microsoft. Section:'Chapter 7, "Running with Least Privilege" Page 207'. Published on 2002.
NIST .Federal Desktop Core Configuration.
Michael Howard David LeBlanc John Viega .24 Deadly Sins of Software Security. McGraw-Hill. Section:'"Sin 16: Executing Code With Too Much Privilege." Page 243'. Published on 2010.
Mark Dowd John McDonald Justin Schuh .The Art of Software Security Assessment 1st Edition. Addison Wesley. Section:'Chapter 9, "Privilege Vulnerabilities", Page 477.'. Published on 2006.


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