CVE-2007-4091 in rsync
Summary
by MITRE
Multiple off-by-one errors in the sender.c in rsync 2.6.9 might allow remote attackers to execute arbitrary code via directory names that are not properly handled when calling the f_name function.
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Analysis
by VulDB Data Team • 03/15/2021
The vulnerability identified as CVE-2007-4091 represents a critical security flaw in the rsync file synchronization utility version 2.6.9, specifically within the sender.c component that handles directory name processing. This issue stems from multiple off-by-one errors that occur during the f_name function invocation when processing directory names, creating a condition where attackers can manipulate input data to trigger memory corruption. The vulnerability exists in the boundary checking mechanisms that fail to properly validate the length and structure of directory names, allowing for potential buffer overflow conditions that could be exploited remotely.
The technical implementation of this vulnerability exploits the fundamental flaw in how rsync processes directory names during the synchronization process. When directory names exceed expected length parameters or contain specific character sequences, the off-by-one errors cause the application to write beyond allocated memory boundaries, potentially overwriting adjacent memory locations. This memory corruption can be leveraged by remote attackers to execute arbitrary code with the privileges of the rsync process, which typically runs with elevated permissions. The flaw specifically manifests when the f_name function is called with improperly handled directory names, creating a scenario where attacker-controlled data can influence memory layout and execution flow.
The operational impact of this vulnerability extends beyond simple remote code execution, as it can lead to complete system compromise when rsync is running in daemon mode with appropriate permissions. Attackers can craft malicious directory names that, when processed by the vulnerable rsync implementation, cause the application to behave unpredictably and execute malicious code. This vulnerability affects systems where rsync is configured to accept remote connections, particularly those running in server mode with default or insecure configurations. The remote exploitation capability means that attackers do not need physical access to the system, making this vulnerability particularly dangerous in networked environments where rsync services are exposed to untrusted networks.
Mitigation strategies for CVE-2007-4091 should prioritize immediate patching of affected rsync installations to version 3.0.0 or later, which contains the necessary fixes for the off-by-one errors in sender.c. System administrators should also implement network-level restrictions to limit access to rsync services, particularly disabling daemon mode when not required. Additional protective measures include configuring rsync with strict input validation, monitoring for unusual directory name patterns, and implementing network segmentation to reduce the attack surface. Organizations should also consider implementing intrusion detection systems that can identify potential exploitation attempts based on suspicious rsync protocol interactions. This vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and maps to ATT&CK technique T1059.007 for execution through remote services, highlighting the need for comprehensive security controls beyond simple patching. The vulnerability demonstrates the critical importance of proper input validation and boundary checking in network services, particularly those handling user-provided data in file system operations.