ChestnutCMS up to 1.5.0 API Endpoint /api/member/avatar Base64.getDecoder.decode suffix unrestricted upload

Summaryinfo

A vulnerability was found in ChestnutCMS up to 1.5.0. It has been declared as critical. Affected by this issue is the function Base64.getDecoder.decode of the file /api/member/avatar of the component API Endpoint. Such manipulation of the argument suffix leads to unrestricted upload. This vulnerability is traded as CVE-2024-56828. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in ChestnutCMS up to 1.5.0. Affected by this issue is the function Base64.getDecoder.decode of the file /api/member/avatar of the component API Endpoint. The manipulation of the argument suffix with an unknown input leads to a unrestricted upload vulnerability. Using CWE to declare the problem leads to CWE-434. The product allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment. Impacted is confidentiality, integrity, and availability. CVE summarizes:

File Upload vulnerability in ChestnutCMS through 1.5.0. Based on the code analysis, it was determined that the /api/member/avatar API endpoint receives a base64 string as input. This string is then passed to the memberService.uploadAvatarByBase64 method for processing. Within the service, the base64-encoded image is parsed. For example, given a string like: data:image/html;base64,PGh0bWw+PGltZyBzcmM9eCBvbmVycm9yPWFsZXJ0KDEpPjwvaHRtbD4= the content after the comma is extracted and decoded using Base64.getDecoder().decode(). The substring from the 11th character up to the first occurrence of a semicolon (;) is assigned to the suffix variable (representing the file extension). The decoded content is then written to a file. However, the file extension is not validated, and since this functionality is exposed to the frontend, it poses significant security risks.

This vulnerability is handled as CVE-2024-56828 since 01/02/2025. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/23/2025). The MITRE ATT&CK project declares the attack technique as T1608.002.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2024-53439). Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• ChestnutCMS

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5.0

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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