Listen to this Post
The vulnerability resides in the thumb.cgi component of Synology FileStation, which handles thumbnail generation for image files. Authenticated remote users can send HTTP requests to this CGI endpoint with manipulated parameters. Specifically, the ‘file’ or path parameters lack proper input validation and sanitization, allowing path traversal sequences. Attackers can inject directory traversal strings such as “../” to access arbitrary files outside the intended directory. The CGI script fails to enforce adequate access controls, trusting authenticated sessions without verifying file-level permissions. This enables read operations on any image file, and under certain conditions, write operations to modify existing files. The flaw stems from insecure handling of user-supplied input in file system operations within the thumbnailing functionality. By crafting a malicious request, an attacker can specify absolute paths or relative paths to sensitive system files. Exploitation requires valid user credentials, but any authenticated account, even with low privileges, can potentially trigger the vulnerability. The issue allows disclosure of confidential data, including password files or application configurations. Additionally, writing to image files could corrupt data or plant malicious content for further attacks. If writable directories are accessible, it might lead to remote code execution by uploading script files. Synology DSM versions prior to the patch are affected across multiple models. The vulnerability was discovered through security research and reported to Synology. Patches address the flaw by implementing strict input validation and path canonicalization. Users must update to fixed DSM releases to mitigate the risk. The CVSS score reflects high severity due to the combination of data breach and system compromise potentials.
Platform: Synology FileStation
Version: Pre-patch DSM
Vulnerability: Arbitrary file read/write
Severity: Critical
date: 2025-12-04
Prediction: Patch released 2025-12-05
What Undercode Say:
curl -k -H "Cookie: id=VALID_SESSION" "https://TARGET/webman/thumb.cgi?file=../../etc/passwd"
nmap -p 443 --script http-synology-thumb-cve TARGET
grep -r "thumb.cgi" /var/log/nginx/access.log
how Exploit:
Authenticate to DSM web interface. Craft GET request to thumb.cgi with traversal payload in file parameter. Use curl or browser to execute request for arbitrary file read/write. Repeat with different paths to access system files.
Protection from this CVE
Apply Synology security update. Restrict FileStation access. Enforce strong authentication. Monitor CGI requests.
Impact:
Data confidentiality loss. System file modification. Potential code execution. Service disruption.
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
