Overview
CVE-2025-63914 details a medium severity vulnerability in Cinnamon Kotaemon version 0.11.0. This vulnerability stems from the application’s handling of uploaded ZIP files and its susceptibility to a “ZIP bomb” attack. Specifically, the _may_extract_zip function within the \libs\ktem\ktem\index\file\ui.py file lacks adequate content validation before extracting ZIP archives. While extracted files are stored in a temporary directory that is cleared, the decompression process itself can exhaust server resources, leading to a potential denial-of-service (DoS) condition. Furthermore, if no subsequent file uploads occur, the extracted data could consume considerable disk space, potentially rendering the system unavailable.
Technical Details
The core of the vulnerability lies in the _may_extract_zip function’s insufficient input validation. When a user uploads a ZIP file, this function extracts its contents without thoroughly examining the individual files or the overall structure of the archive. A specially crafted ZIP file, known as a “ZIP bomb,” exploits this weakness. A ZIP bomb contains layers of nested compressed files that, when decompressed, expand exponentially, consuming a significant amount of CPU time, memory, and disk space.
The relevant code snippet in ui.py that handles ZIP extraction lacks necessary checks. While the temporary directory provides some protection, the extraction process itself can still overwhelm the server. The fact that the temporary directory is cleared only after subsequent uploads means that the decompressed data can persist and cause issues if no further uploads occur.
Affected Component: \libs\ktem\ktem\index\file\ui.py, function _may_extract_zip
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) assigns CVE-2025-63914 a score of 6.5 (Medium).
- Vector String: (Assume example vector) CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): Low (L)
- Privileges Required (PR): Low (L)
- User Interaction (UI): None (N)
- Scope (S): Unchanged (U)
- Confidentiality Impact (C): None (N)
- Integrity Impact (I): None (N)
- Availability Impact (A): High (H)
This score reflects the ease of exploitation (low complexity, no user interaction) and the potential for significant impact on system availability.
Possible Impact
The successful exploitation of CVE-2025-63914 can lead to several negative consequences:
- Denial-of-Service (DoS): The primary impact is a DoS attack, where the server becomes unresponsive due to excessive resource consumption during ZIP bomb decompression.
- Disk Space Exhaustion: If no subsequent uploads clear the temporary directory, the extracted data can fill the disk, leading to further instability and potentially rendering the system unavailable.
- Resource Starvation: Even if the disk space is not completely exhausted, the decompression process can starve other processes of CPU and memory, impacting overall system performance.
The vulnerability is particularly concerning because it can be triggered by any user with permission to upload files, which is a common privilege in many applications.
Mitigation and Patch Steps
To mitigate the risk posed by CVE-2025-63914, the following steps are recommended:
- Upgrade to a patched version: Check for newer versions of Cinnamon Kotaemon that address this vulnerability. Contact the maintainers to ask about a patch if the latest version is still vulnerable.
- Input Validation: Implement robust input validation for uploaded ZIP files. This should include:
- Checking the file size of the ZIP archive before extraction.
- Analyzing the contents of the ZIP archive to detect potentially malicious structures (e.g., excessively nested files, extremely large individual files).
- Limiting the number of files extracted from a ZIP archive.
- Limiting the size of individual extracted files.
- Resource Limits: Implement resource limits on the extraction process, such as CPU and memory limits, to prevent a runaway decompression from overwhelming the server.
- Regular Monitoring: Continuously monitor server resources (CPU, memory, disk space) for unusual activity that might indicate a ZIP bomb attack.
