CWE-250: Execution with Unnecessary Privileges

Description

The product 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.

ThreatScore

Threat Mapped score: 0.0

Industry: Finiancial

Threat priority: Unclassified

Observed Examples (CVEs)

CVE: 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: CVE-2008-1877

Program runs with privileges and calls another program with the same privileges, which allows read of arbitrary files.
CVE: CVE-2007-5159

OS incorrectly installs a program with setuid privileges, allowing users to gain privileges.
CVE: CVE-2008-4638

Composite: application running with high privileges (CWE-250) allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file (CWE-209).
CVE: CVE-2008-0162

Program does not drop privileges before calling another program, allowing code execution.
CVE: CVE-2008-0368

setuid root program allows creation of arbitrary files through command line argument.
CVE: CVE-2007-3931

Installation script installs some programs as setuid when they shouldn't be.
CVE: CVE-2020-3812

mail program runs as root but does not drop its privileges before attempting to access a file. Attacker can use a symlink from their home directory to a directory only readable by root, then determine whether the file exists based on the response.
CVE: CVE-2003-0908

Product launches Help functionality while running with raised privileges, allowing command execution using Windows message to access "open file" dialog.

Related Attack Patterns (CAPEC)

Attack TTPs

N/A

Modes of Introduction

Phase	Note
Implementation	REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Installation	N/A
Architecture and Design	If an application has this design problem, then it can be easier for the developer to make implementation-related errors such as CWE-271 (Privilege Dropping / Lowering Errors). In addition, the consequences of Privilege Chaining (CWE-268) can become more severe.
Operation	N/A

Common Consequences

Impact: Gain Privileges or Assume Identity, Execute Unauthorized Code or Commands, Read Application Data, DoS: Crash, Exit, or Restart — Notes: 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.

Potential Mitigations

Architecture and Design: 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. (N/A)
Architecture and Design: 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 [REF-76]. 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. (N/A)
Architecture and Design: 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 [REF-76]. 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. (N/A)
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. (N/A)
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. (N/A)
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 [REF-76]. 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. (N/A)
Operation: Ensure that the software runs properly under the United States Government Configuration Baseline (USGCB) [REF-199] or an equivalent hardening configuration guide, which many organizations use to limit the attack surface and potential risk of deployed software. (N/A)

Applicable Platforms

None (Not Language-Specific, Undetermined)

Demonstrative Examples

Intro: This code temporarily raises the program's privileges to allow creation of a new user folder.

Body: While the program only raises its privilege level to create the folder and immediately lowers it again, if the call to os.mkdir() throws an exception, the call to lowerPrivileges() will not occur. As a result, the program is indefinitely operating in a raised privilege state, possibly allowing further exploitation to occur.

def makeNewUserDir(username): if invalidUsername(username): #avoid CWE-22 and CWE-78 print('Usernames cannot contain invalid characters') return False try: raisePrivileges() os.mkdir('/home/' + username) lowerPrivileges() except OSError: print('Unable to create new user directory for user:' + username) return False return True

Intro: The following code calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.

Body: Constraining the process inside the application's home directory before opening any files is a valuable security measure. However, the absence of a call to setuid() with some non-zero value means the application is continuing to operate with unnecessary root privileges. Any successful exploit carried out by an attacker against the application can now result in a privilege escalation attack because any malicious operations will be performed with the privileges of the superuser. If the application drops to the privilege level of a non-root user, the potential for damage is substantially reduced.

chroot(APP_HOME); chdir("/"); FILE* data = fopen(argv[1], "r+"); ...

Intro: This application intends to use a user's location to determine the timezone the user is in:

Body: This is unnecessary use of the location API, as this information is already available using the Android Time API. Always be sure there is not another way to obtain needed information before resorting to using the location API.

locationClient = new LocationClient(this, this, this); locationClient.connect(); Location userCurrLocation; userCurrLocation = locationClient.getLastLocation(); setTimeZone(userCurrLocation);

Intro: This code uses location to determine the user's current US State location.

Body: First the application must declare that it requires the ACCESS_FINE_LOCATION permission in the application's manifest.xml:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

Notes

Relationship: 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.
Maintenance: CWE-271, CWE-272, and CWE-250 are all closely related and possibly overlapping. CWE-271 is probably better suited as a category. Both CWE-272 and CWE-250 are in active use by the community. The "least privilege" phrase has multiple interpretations.
Maintenance: The Taxonomy_Mappings to ISA/IEC 62443 were added in CWE 4.10, but they are still under review and might change in future CWE versions. These draft mappings were performed by members of the "Mapping CWE to 62443" subgroup of the CWE-CAPEC ICS/OT Special Interest Group (SIG), and their work is incomplete as of CWE 4.10. The mappings are included to facilitate discussion and review by the broader ICS/OT community, and they are likely to change in future CWE versions.

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