Summary
H3C CVM contains an unauthenticated arbitrary file upload vulnerability in its file upload endpoint. An attacker may use path traversal in the caller-supplied token parameter to place a server-side script in a web-accessible location, potentially resulting in remote code execution as the web-server user.
Affected context
The issue occurs in H3C CVM deployments where the /cas/fileUpload/upload endpoint is reachable and does not require authentication. Risk is increased when the endpoint accepts caller-controlled path information, does not constrain uploaded file types, and stores files in directories that the web server can access or execute.
Exploit preconditions
- Attack surface: The H3C CVM file upload endpoint
- Required access: Network access to the endpoint; authentication may not be required
- Trigger point: Processing an upload request containing a manipulated token value
- Why exploitation is possible: The endpoint may use caller-controlled path information without effective traversal protection or file-type restrictions, allowing uploaded content to reach a web-accessible location
Why this happens
The vulnerability results from treating upload metadata and destination paths supplied by the caller as trustworthy. Insufficient path canonicalization, destination validation, and file-type enforcement can allow an attacker to store executable server-side content outside the intended upload directory. This behavior maps to CWE-434: Unrestricted Upload of File with Dangerous Type.
Potential impact
- An attacker may execute arbitrary code with the privileges of the web-server process
- The application or underlying host could be compromised
- Sensitive cloud-management data may be accessed or altered
- The attacker could use the compromised service for lateral movement
- Cloud workloads or management operations may be disrupted
General mitigation guidance
Mitigation generally focuses on making file uploads non-executable and reducing trust in all client-controlled upload metadata.
Common defensive patterns include:
- Allowing only narrowly defined file types based on server-side content validation
- Generating server-side filenames and ignoring caller-supplied paths or names
- Canonicalizing paths and enforcing containment within a dedicated upload directory
- Storing uploads outside web roots or serving them through a non-executable content path
- Applying explicit size, extension, MIME, and content-signature limits
- Requiring authentication and authorization for administrative upload functions
- Running web services with least privilege and restricting write permissions
- Separating uploaded content from sensitive application and management data
How teams detect issues like this
High-level detection approaches include:
- Static analysis for upload handlers that concatenate user input into filesystem paths
- Code review checks for missing canonicalization, allowlists, or server-generated filenames
- Monitoring upload requests for traversal indicators, unexpected extensions, and writes outside approved directories
- Reviewing web-server logs for requests to newly created or uploaded server-side files
- Enforcing policy rules that prevent executable content from being stored under web-accessible paths
- Using automated security review tools to identify unrestricted upload patterns
