1. What is this vulnerability and why does it matter?

This vulnerability, identified as CVE-2022-25299, affects the Cesanta Mongoose library. It is an arbitrary file write vulnerability stemming from the unsafe handling of file names during the upload process using the `mg_http_upload()` method. This allows an attacker to bypass intended file storage locations.

This vulnerability matters significantly because it enables attackers to write files to arbitrary locations outside the designated target folder. Such an action can have severe consequences, including:

• Uploading and executing malicious scripts (e.g., web shells), leading to remote code execution.
• Overwriting critical system files, causing denial of service or system corruption.
• Injecting unauthorized content or configurations.

The existence of published active exploits for this vulnerability further elevates its importance and the urgency for remediation, as it indicates a real and present threat to affected systems.

2. What are the CVSS score, severity level, and disclosure details?

The CVSS score for CVE-2022-25299 is 7.5.

The severity level associated with a CVSS score of 7.5 is classified as High.

Disclosure Details:

• Published Date: 2022-02-18 12:55:21
• Last Modified Date: 2024-09-16 17:52:54

3. Which products, vendors, systems, and versions are affected?

4. What is the technical root cause and attack vector?

The technical root cause of CVE-2022-25299 is the unsafe handling of file names during file upload operations within the Cesanta Mongoose library. Specifically, the `mg_http_upload()` method fails to properly sanitize or validate file names provided by an attacker.

The attack vector involves an attacker crafting a malicious filename that includes directory traversal sequences (e.g., `../`, `..\`) when performing a file upload. This exploit leverages the CWE-552 (Files or Directories Accessible to External Parties) weakness, where the application incorrectly trusts user-supplied data to determine file paths.

5. How can this vulnerability be exploited?

This vulnerability can be exploited by an attacker submitting a specially crafted HTTP POST request that utilizes the `mg_http_upload()` method for file uploads. The attacker manipulates the filename parameter within the upload request to include path traversal sequences, such as `../` (dot-dot-slash) or `..\` (dot-dot-backslash).

When the vulnerable Mongoose application processes this filename, instead of storing the file within the intended target directory, the directory traversal sequences cause the application to write the uploaded file to an arbitrary location on the file system determined by the attacker.

For instance, an attacker might upload a file named `../../../../etc/malicious_config.conf` or `../../../../var/www//webshell.php`. If successful, this can lead to:

• Arbitrary file creation or overwriting.
• Placement of malicious web shells for remote code execution.
• Corruption of critical configuration or data files.

It is known that active exploits have been published, indicating that the methods for exploitation are publicly available and potentially actively used by threat actors.

6. What mitigation steps and patches are available?

The primary mitigation step for CVE-2022-25299 is to upgrade Cesanta Mongoose to a patched version.

• Patch: Upgrade to Mongoose version 7.6 or later. This version addresses the unsafe file name handling issue.
• Workaround (if immediate patching is not possible): Implement robust input validation and sanitization for all file upload functionalities. Specifically, ensure that filenames are stripped of any directory traversal characters (e.g., `../`, `..\`) and that the final resolved path is strictly confined to an allowed upload directory. It is strongly recommended to use a whitelist approach for allowed characters in filenames and to always resolve and validate the absolute path before writing any files.

7. How can vulnerable systems be detected?

Vulnerable systems can be detected by identifying the version of the Cesanta Mongoose library deployed within an application or system.

Detection methods include:

• Version Check: Inspect the Mongoose library files or application configuration to determine the installed version. Any version number prior to 7.6 is vulnerable.
• Software Bill of Materials (SBOM): If an SBOM is maintained for the application, it should list the version of Mongoose in use, allowing for easy identification of vulnerable instances.

8. What are the indicators of compromise (IOCs)?

The provided CVE data does not specify any direct Indicators of Compromise (IOCs) for CVE-2022-25299. However, potential IOCs could include:

• Presence of unauthorized files or directories outside expected upload paths.
• Unusual file write activity to sensitive system directories.
• Logs showing suspicious file upload requests with path traversal sequences in filenames.
• Unexplained execution of unfamiliar scripts or processes on the server.

9. Which threat actors are known to exploit this vulnerability?

While the CVE data confirms that active exploits have been published for CVE-2022-25299, it does not name specific threat actors, groups, or individuals known to be exploiting this vulnerability. The presence of public exploits suggests that a wide range of actors, from opportunistic attackers to more sophisticated groups, may attempt to leverage this flaw.

10. What public intelligence references and advisories exist?

The primary public intelligence reference for this vulnerability is its CVE identifier: CVE-2022-25299. This identifier serves as a central point for information published by various security entities.

Organizations involved in cybersecurity research and vulnerability management typically publish advisories and intelligence based on CVE entries. It is recommended to consult official advisories from Cesanta (the vendor) and major cybersecurity databases for the most up-to-date and detailed information.

11. What is the risk assessment and urgency level?

Risk Assessment:
The risk associated with CVE-2022-25299 is assessed as High. This assessment is based on several factors:

• CVSS Score: A CVSS score of 7.5 indicates a high severity vulnerability.
• Impact: The vulnerability allows for arbitrary file write, which can directly lead to severe consequences such as remote code execution, full system compromise, denial of service, or data manipulation.
• Ease of Exploitation: Path traversal vulnerabilities are often straightforward to exploit with readily available tools and techniques.

Urgency Level:
The urgency level for addressing this vulnerability is High. This is critically elevated due to the explicit mention that active exploits have been published. This means that the methods to exploit this flaw are publicly known and potentially being leveraged by threat actors. Organizations using affected versions of Cesanta Mongoose are under immediate threat and should prioritize patching or implementing mitigating controls without delay.