Overview
CVE-2025-10158 describes a medium-severity vulnerability affecting the rsync file transfer utility. A malicious client, acting as the receiver of an rsync transfer, can exploit this flaw to trigger an out-of-bounds read of a heap-based buffer. This occurs due to a negative array index within the rsync code when processing data sent from the server. Successful exploitation requires the attacker to have at least read access to the remote rsync module being transferred.
Technical Details
The vulnerability stems from how rsync handles array indexing when processing data during file transfer reception. Specifically, a carefully crafted, malicious rsync client can send data to the server that, upon processing, leads to a negative index being used to access a heap-based buffer. This negative index causes the program to read memory outside of the intended buffer boundaries, resulting in an out-of-bounds read. The specifics of the code affected involves the interpretation of array index when a client recieves the file via the rsync protocol.
The impact of this vulnerability is that an attacker could potentially glean sensitive information from the server’s memory. This could include configuration data, cryptographic keys, or other sensitive data present in memory at the time of the exploit.
CVSS Analysis
The vulnerability has been assigned a CVSS score of 4.3 (Medium). The CVSS vector is likely something like CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N. This score reflects the relatively low attack complexity and the need for the attacker to have read access to the rsync module. While a successful exploit could lead to information disclosure, it doesn’t allow for remote code execution or modification of data.
Possible Impact
Exploitation of CVE-2025-10158 can lead to:
- Information Disclosure: Sensitive data stored in server memory, such as configuration files, API keys, or even other application data, may be exposed to the attacker.
- Data Leakage: The attacker could potentially extract valuable information, leading to further attacks or compromise of the affected system.
- Potential for Chained Exploits: While the out-of-bounds read itself doesn’t provide code execution, the disclosed information could be used in conjunction with other vulnerabilities to achieve a more severe compromise.
Mitigation and Patch Steps
The primary mitigation step is to apply the patch provided by the Rsync Project. Users should update their rsync installations to a version that includes the fix for commit 797e17fc4a6f15e3b1756538a9f812b63942686f. This commit addresses the negative array index issue, preventing the out-of-bounds read.
Until the patch can be applied, consider the following temporary mitigations:
- Restrict Access: Limit access to rsync modules to only trusted clients.
- Monitor Rsync Activity: Implement monitoring to detect unusual rsync activity that might indicate an attempted exploit.
Regularly check for security updates from the Rsync Project and apply them promptly to ensure your systems are protected against known vulnerabilities.