Google Cloud Researchers Uncover Flaws in Rsync File Synchronization Tool

January 15, 2025

As many as six security vulnerabilities have been disclosed in the popular Rsync file-synchronizing tool for Unix systems, some of which could be exploited to execute arbitrary code on a client.

"Attackers can take control of a malicious server and read/write arbitrary files of any connected client," the CERT Coordination Center (CERT/CC) said in an advisory. "Sensitive data, such as SSH keys, can be extracted, and malicious code can be executed by overwriting files such as ~/.bashrc or ~/.popt."

The shortcomings, which comprise heap-buffer overflow, information disclosure, file leak, external directory file-write, and symbolic-link race condition, are listed below -

CVE-2024-12084 (CVSS score: 9.8) - Heap-buffer overflow in Rsync due to improper checksum length handling
CVE-2024-12085 (CVSS score: 7.5) - Information leak via uninitialized stack contents
CVE-2024-12086 (CVSS score: 6.1) - Rsync server leaks arbitrary client files
CVE-2024-12087 (CVSS score: 6.5) - Path traversal vulnerability in Rsync
CVE-2024-12088 (CVSS score: 6.5) - --safe-links option bypass leads to path traversal
CVE-2024-12747 (CVSS score: 5.6) - Race condition in Rsync when handling symbolic links

Simon Scannell, Pedro Gallegos, and Jasiel Spelman from Google Cloud Vulnerability Research have been credited with discovering and reporting the first five flaws. Security researcher Aleksei Gorban has been acknowledged for the symbolic-link race condition flaw.

"In the most severe CVE, an attacker only requires anonymous read access to a Rsync server, such as a public mirror, to execute arbitrary code on the machine the server is running on," Red Hat Product Security's Nick Tait said.

CERT/CC also noted that an attacker could combine CVE-2024-12084 and CVE-2024-12085 to achieve arbitrary code execution on a client that has a Rsync server running.

Patches for the vulnerabilities have been released in Rsync version 3.4.0, which was made available earlier today. For users who are unable to apply the update, the following mitigations are recommended -

CVE-2024-12084 - Disable SHA* support by compiling with CFLAGS=-DDISABLE_SHA512_DIGEST and CFLAGS=-DDISABLE_SHA256_DIGEST
CVE-2024-12085 - Compile with -ftrivial-auto-var-init=zero to zero the stack contents