CVE-2025-11624 Overview
CVE-2025-11624 is a stack buffer overwrite vulnerability affecting the wolfSSH SFTP server component. The vulnerability occurs when the server receives a malicious packet containing a handle size that exceeds the system handle or file descriptor size but remains smaller than the maximum allowed handle size. This boundary condition error can lead to memory corruption on the server side.
Critical Impact
Malicious SFTP packets with crafted handle sizes can trigger stack buffer overwrites on wolfSSH servers, potentially affecting system stability and data integrity.
Affected Products
- wolfSSH (all versions prior to the fix)
Discovery Timeline
- 2025-10-21 - CVE-2025-11624 published to NVD
- 2025-12-04 - Last updated in NVD database
Technical Details for CVE-2025-11624
Vulnerability Analysis
This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption issue that occurs during SFTP packet processing. The root cause lies in insufficient validation of handle size parameters within incoming SFTP packets. When a malicious packet specifies a handle size that falls between the actual system handle/file descriptor size and the maximum permitted handle size, the server writes data beyond the intended stack buffer boundaries.
The vulnerability requires network access to exploit, as an attacker must be able to send specially crafted SFTP packets to the vulnerable server. However, exploitation requires high privileges and active user interaction, significantly limiting the practical attack surface.
Root Cause
The vulnerability stems from inadequate boundary checking in the SFTP packet handling routines. The server fails to properly validate that the incoming handle size matches the expected system handle or file descriptor size. Instead, it only checks against the maximum allowed handle size, creating a gap where oversized (but not maximum-sized) handles can cause stack buffer overwrites.
Attack Vector
An attacker with network access to a wolfSSH SFTP server can craft malicious SFTP packets containing handle sizes that exceed the system's native handle size but fall below the maximum permitted handle size. When the server processes these packets, it attempts to write handle data into a stack buffer sized for the smaller system handles, resulting in a stack buffer overwrite.
The attack requires:
- Network connectivity to the SFTP server
- High-level privileges on the target system
- Active user interaction
The vulnerability allows potential low-impact compromise of confidentiality, integrity, and availability on the vulnerable system.
Detection Methods for CVE-2025-11624
Indicators of Compromise
- Unexpected crashes or instability in wolfSSH SFTP server processes
- Anomalous SFTP packets with unusual handle size values in network traffic logs
- Memory corruption indicators or stack smashing detected messages in system logs
Detection Strategies
- Monitor SFTP server processes for unexpected termination or restart patterns
- Implement network intrusion detection rules to identify SFTP packets with abnormally large handle size fields
- Enable memory protection mechanisms such as stack canaries and ASLR to detect exploitation attempts
Monitoring Recommendations
- Review wolfSSH SFTP server logs for any signs of malformed packet handling
- Implement network traffic analysis focused on SFTP protocol anomalies
- Configure alerting for wolfSSH process crashes or unexpected behavior
How to Mitigate CVE-2025-11624
Immediate Actions Required
- Update wolfSSH to the latest version that includes the security fix
- Review network access controls to limit SFTP server exposure
- Enable stack protection mechanisms on systems running wolfSSH
Patch Information
The vulnerability has been addressed in GitHub Pull Request #834. Organizations should update to the patched version of wolfSSH that incorporates this fix to remediate the vulnerability.
Workarounds
- Restrict network access to the SFTP server to trusted IP addresses only
- Implement firewall rules to limit SFTP connections to authorized clients
- Monitor SFTP server processes closely for any signs of instability while awaiting patch deployment
- Consider temporarily disabling SFTP functionality if it is not business-critical
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
