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Weakness · High

CWE-732: Incorrect Permission Assignment for Critical Resource

What it is

The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.

Likelihood of exploit: High2 exploited in the wildMITRE CWE 4.19.1

Severity (our rating)
High
Likelihood of exploit
High
Introduced during
Architecture and Design, Implementation, Installation, Operation
Exploited in the wild
2 known exploited CVEs

In more detail

When a resource is given a permission setting that provides access to a wider range of actors than required, it could lead to the exposure of sensitive information, or the modification of that resource by unintended parties. This is especially dangerous when the resource is related to program configuration, execution, or sensitive user data. For example, consider a misconfigured storage account for the cloud that can be read or written by a public or anonymous user.

What an attacker can do

  • Read Application Data (Confidentiality)
  • Read Files or Directories (Confidentiality)
  • Gain Privileges or Assume Identity (Access Control)
  • Modify Application Data (Integrity, Other)
  • Other (Integrity, Other)

How to prevent it

Implementation

  • When using a critical resource such as a configuration file, check to see if the resource has insecure permissions (such as being modifiable by any regular user), and generate an error or even exit the software if there is a possibility that the resource could have been modified by an unauthorized party.
  • During program startup, explicitly set the default permissions or umask to the most restrictive setting possible. Also set the appropriate permissions during program installation. This will prevent you from inheriting insecure permissions from any user who installs or runs the program.
  • When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.

Architecture and Design

  • Divide the software into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully defining distinct user groups, privileges, and/or roles. Map these against data, functionality, and the related resources. Then set the permissions accordingly. This will allow you to maintain more fine-grained control over your resources.
  • Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software. OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.

System Configuration

  • For all configuration files, executables, and libraries, make sure that they are only readable and writable by the software's administrator.

Documentation

  • Do not suggest insecure configuration changes in documentation, especially if those configurations can extend to resources and other programs that are outside the scope of the application.

Installation

  • Do not assume that a system administrator will manually change the configuration to the settings that are recommended in the software's manual.

Operation

  • Ensure that the software runs properly under the United States Government Configuration Baseline (USGCB) or an equivalent hardening configuration guide, which many organizations use to limit the attack surface and potential risk of deployed software.

How to find it

  • Automated Static Analysis. Automated static analysis may be effective in detecting permission problems for system resources such as files, directories, shared memory, device interfaces, etc. Automated techniques may be able to detect the use of library functions that modify permissions, then analyze function calls for arguments that contain potentially insecure values. However, since the software's intended security policy might allow loose permissions for certain operations (such as publishing a file on a web server), automated static analysis may produce some false positives - i.e., warnings that do not have any security consequences or require any code changes. When custom permissions models are used - such as defining who can read messages in a particular forum in a bulletin board system - these can be difficult to detect using automated static analysis. It may be possible to define custom signatures that identify any custom functions that implement the permission checks and assignments.
  • Automated Dynamic Analysis. Automated dynamic analysis may be effective in detecting permission problems for system resources such as files, directories, shared memory, device interfaces, etc. However, since the software's intended security policy might allow loose permissions for certain operations (such as publishing a file on a web server), automated dynamic analysis may produce some false positives - i.e., warnings that do not have any security consequences or require any code changes. When custom permissions models are used - such as defining who can read messages in a particular forum in a bulletin board system - these can be difficult to detect using automated dynamic analysis. It may be possible to define custom signatures that identify any custom functions that implement the permission checks and assignments.
  • 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.
  • Manual Static Analysis. Manual static analysis may be effective in detecting the use of custom permissions models and functions. The code could then be examined to identifying usage of the related functions. Then the human analyst could evaluate permission assignments in the context of the intended security model of the software.
  • Manual Dynamic Analysis. Manual dynamic analysis may be effective in detecting the use of custom permissions models and functions. The program could then be executed with a focus on exercising code paths that are related to the custom permissions. Then the human analyst could evaluate permission assignments in the context of the intended security model of the software.
  • Fuzzing. Fuzzing is not effective in detecting this weakness.
  • 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 watch for library functions or system calls on OS resources such as files, directories, and shared memory. Examine the arguments to these calls to infer which permissions are being used.
  • Automated Static Analysis - Binary or Bytecode. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Inter-application Flow Analysis
  • Manual Static Analysis - Binary or Bytecode. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies
  • Dynamic Analysis with Automated Results Interpretation. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Host-based Vulnerability Scanners - Examine configuration for flaws, verifying that audit mechanisms work, ensure host configuration meets certain predefined criteria Web Application Scanner Web Services Scanner Database Scanners
  • Dynamic Analysis with Manual Results Interpretation. According to SOAR, the following detection techniques may be useful: Highly cost effective: Host Application Interface Scanner Cost effective for partial coverage: Fuzz Tester Framework-based Fuzzer Automated Monitored Execution Forced Path Execution
  • Manual Static Analysis - Source Code. According to SOAR, the following detection techniques may be useful: Highly cost effective: Manual Source Code Review (not inspections) Cost effective for partial coverage: Focused Manual Spotcheck - Focused manual analysis of source
  • Automated Static Analysis - Source Code. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Context-configured Source Code Weakness Analyzer
  • Automated Static Analysis. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Configuration Checker
  • Architecture or Design Review. According to SOAR, the following detection techniques may be useful: Highly cost effective: Formal Methods / Correct-By-Construction Cost effective for partial coverage: Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

CWE-732 on MITRE's CWE site

Exploited in the wild: 2 CVEs

Vulnerabilities caused by CWE-732 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.

All known exploited vulnerabilities

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Source: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.