CVE-2026-44508 in rsync
Summary
by MITRE • 07/21/2026
Rsync is a file-copying tool that uses a delta-transfer algorithm to synchronize remote and local files. In versions prior to 3.4.3, the receiver's compressed-token decoder accumulated a 32-bit signed counter without checking for overflow. A malicious sender can trigger an overflow that with careful manipulation can lead to the extraction of data stored in memory of the process allowing an attacker to access environment variables, passwords and memory pointers from the heap, stack, and libraries. The leakage of these pointers and data can significantly reduce the effectiveness of ASLR and facilitate further exploitation. This issue is fixed in version 3.4.3.
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Analysis
by VulDB Data Team • 07/21/2026
The rsync vulnerability represents a critical memory safety issue affecting versions prior to 3.4.3, where the receiver component's compressed-token decoder contains a flaw in its 32-bit signed counter implementation. This vulnerability falls under the category of integer overflow as classified by CWE-190, specifically involving signed integer overflow that can lead to unpredictable behavior and potential information disclosure. The flaw occurs during the decompression process when rsync receives data from a remote source, creating a scenario where malicious input can manipulate internal state variables.
The technical implementation of this vulnerability stems from the receiver component's failure to validate counter overflow conditions during compressed token processing. When a malicious sender crafts specific payloads that trigger the 32-bit signed integer overflow, the system's internal accounting mechanism becomes compromised. The overflow condition allows for controlled manipulation of memory layout information, potentially enabling attackers to extract sensitive data stored in various memory segments including heap, stack, and library areas. This type of vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage and T1068 for exploit for privilege escalation through memory corruption.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked memory pointers and data significantly weaken security mechanisms such as Address Space Layout Randomization. The exposure of environment variables, passwords, and memory addresses provides attackers with crucial information needed to bypass modern security protections. This leakage can facilitate more sophisticated attacks including return-oriented programming (ROP) chains and other exploitation techniques that rely on knowing memory layout details. The vulnerability demonstrates how seemingly minor implementation flaws in network protocols can create substantial security risks.
Mitigation strategies should focus on upgrading to rsync version 3.4.3 or later, which includes proper overflow checking mechanisms for the compressed-token decoder. Organizations should also implement network segmentation and access controls to limit exposure of rsync services to trusted networks only. Additional defensive measures include monitoring for unusual rsync traffic patterns and implementing intrusion detection systems that can identify potential exploitation attempts. The fix implemented in version 3.4.3 addresses the root cause by adding proper bounds checking to prevent the counter overflow condition, thereby eliminating the information disclosure vector while maintaining normal operational functionality.