Description
Rust is a programming language. The Rust Security Response WG was notified that the Rust standard library prior to version 1.77.2 did not properly escape arguments when invoking batch files (with the `bat` and `cmd` extensions) on Windows using the `Command`. An attacker able to control the arguments passed to the spawned process could execute arbitrary shell commands by bypassing the escaping. The severity of this vulnerability is critical for those who invoke batch files on Windows with untrusted arguments. No other platform or use is affected. The `Command::arg` and `Command::args` APIs state in their documentation that the arguments will be passed to the spawned process as-is, regardless of the content of the arguments, and will not be evaluated by a shell. This means it should be safe to pass untrusted input as an argument. On Windows, the implementation of this is more complex than other platforms, because the Windows API only provides a single string containing all the arguments to the spawned process, and it's up to the spawned process to split them. Most programs use the standard C run-time argv, which in practice results in a mostly consistent way arguments are splitted. One exception though is `cmd.exe` (used among other things to execute batch files), which has its own argument splitting logic. That forces the standard library to implement custom escaping for arguments passed to batch files. Unfortunately it was reported that our escaping logic was not thorough enough, and it was possible to pass malicious arguments that would result in arbitrary shell execution. Due to the complexity of `cmd.exe`, we didn't identify a solution that would correctly escape arguments in all cases. To maintain our API guarantees, we improved the robustness of the escaping code, and changed the `Command` API to return an `InvalidInput` error when it cannot safely escape an argument. This error will be emitted when spawning the process. The fix is included in Rust 1.77.2. Note that the new escaping logic for batch files errs on the conservative side, and could reject valid arguments. Those who implement the escaping themselves or only handle trusted inputs on Windows can also use the `CommandExt::raw_arg` method to bypass the standard library's escaping logic.
EPSS Score:
80%
Comprehensive Technical Analysis of EUVD-2024-21981
1. Vulnerability Assessment and Severity Evaluation
Vulnerability Description:
The vulnerability affects the Rust standard library prior to version 1.77.2. Specifically, it involves improper escaping of arguments when invoking batch files (with .bat and .cmd extensions) on Windows using the Command API. This flaw allows an attacker to execute arbitrary shell commands by bypassing the intended escaping mechanism.
Severity Evaluation:
The vulnerability is rated with a CVSS base score of 10.0, indicating a critical severity. The CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H highlights the following characteristics:
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): Low (L)
- Privileges Required (PR): None (N)
- User Interaction (UI): None (N)
- Scope (S): Changed (C)
- Confidentiality (C): High (H)
- Integrity (I): High (H)
- Availability (A): High (H)
This high severity is due to the potential for remote code execution, which can lead to significant impacts on confidentiality, integrity, and availability.
2. Potential Attack Vectors and Exploitation Methods
Attack Vectors:
- Remote Code Execution (RCE): An attacker can exploit this vulnerability by crafting malicious arguments that bypass the escaping logic, leading to arbitrary shell command execution.
- Command Injection: By manipulating the arguments passed to the
CommandAPI, an attacker can inject commands that will be executed by the shell.
Exploitation Methods:
- Untrusted Input: If an application accepts untrusted input and passes it to the
CommandAPI without proper validation, an attacker can exploit this vulnerability. - Batch File Execution: The vulnerability is specific to the execution of batch files on Windows, making any application that invokes batch files with user-supplied arguments a potential target.
3. Affected Systems and Software Versions
Affected Systems:
- Windows operating systems where Rust applications invoke batch files using the
CommandAPI.
Affected Software Versions:
- Rust standard library versions prior to 1.77.2.
4. Recommended Mitigation Strategies
Immediate Mitigation:
- Upgrade Rust: Upgrade to Rust version 1.77.2 or later, which includes the fix for this vulnerability.
- Input Validation: Ensure that all inputs passed to the
CommandAPI are properly validated and sanitized. - Use
CommandExt::raw_arg: For applications that handle trusted inputs or implement their own escaping logic, use theCommandExt::raw_argmethod to bypass the standard library's escaping logic.
Long-Term Mitigation:
- Code Review: Conduct a thorough code review to identify and mitigate similar vulnerabilities in other parts of the codebase.
- Security Training: Provide security training for developers to understand the risks associated with command injection and improper input handling.
5. Impact on European Cybersecurity Landscape
Potential Impact:
- Widespread Adoption: Given the increasing adoption of Rust in critical systems, this vulnerability poses a significant risk to the security of applications developed in Rust.
- Supply Chain Risks: Organizations relying on third-party Rust libraries or applications need to ensure that their dependencies are up-to-date to mitigate this risk.
- Regulatory Compliance: Organizations must comply with regulations such as GDPR, which require robust security measures to protect personal data.
Mitigation Efforts:
- Coordinated Disclosure: The Rust Security Response WG's coordinated disclosure and prompt patching demonstrate a proactive approach to vulnerability management.
- Community Awareness: Increased awareness within the developer community about the importance of secure coding practices and regular updates.
6. Technical Details for Security Professionals
Technical Overview:
- Escaping Logic: The vulnerability arises from insufficient escaping logic in the Rust standard library when handling arguments for batch files on Windows.
- API Changes: The fix includes improved escaping logic and the introduction of an
InvalidInputerror to handle cases where arguments cannot be safely escaped. - Bypass Mechanism: The
CommandExt::raw_argmethod allows developers to bypass the standard library's escaping logic for trusted inputs.
References:
- GitHub Advisory: GHSA-q455-m56c-85mh
- Rust Documentation:
- Security Policies: Rust Security Policies
Conclusion: This vulnerability underscores the importance of robust input handling and escaping mechanisms in programming languages. The Rust community's prompt response and the availability of mitigation strategies highlight the collaborative efforts required to maintain a secure cybersecurity landscape. Organizations and developers should prioritize updating to the latest Rust version and implementing best practices for input validation to mitigate such risks effectively.