CVE-2018-20013 in UrBackup
Summary
by MITRE
In UrBackup 2.2.6, an attacker can send a malformed request to the client over the network, and trigger a fileservplugin/CClientThread.cpp CClientThread::ProcessPacket metadata_id!=0 assertion, leading to shutting down the client application.
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Analysis
by VulDB Data Team • 10/06/2023
The vulnerability identified as CVE-2018-20013 affects UrBackup version 2.2.6, a comprehensive backup solution designed for both Windows and Linux environments. This issue represents a critical software flaw that can be exploited through network-based attacks targeting the client application component. The vulnerability specifically resides within the fileservplugin/CClientThread.cpp file where the CClientThread::ProcessPacket method processes incoming network requests from remote systems. The flaw manifests when an attacker crafts and sends a malformed request to the UrBackup client, which then triggers an assertion failure during packet processing.
The technical implementation of this vulnerability stems from inadequate input validation within the client thread processing logic. When the CClientThread::ProcessPacket method receives a malformed network packet, it fails to properly validate the metadata_id field before proceeding with processing operations. This validation failure results in the assertion metadata_id!=0 being triggered, causing the client application to terminate abruptly. The assertion failure represents a classic buffer over-read or invalid memory access condition that can be exploited to cause a denial of service attack against the backup client. This type of vulnerability falls under the category of assertion failure conditions commonly found in software security assessments and aligns with CWE-617, which addresses reachable assertions that can be triggered by external input.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to systematically compromise backup operations across networks. Attackers can exploit this weakness to repeatedly crash client applications, potentially leading to backup failures and data loss scenarios. The vulnerability affects both Windows and Linux clients, making it particularly dangerous in mixed environments where administrators may not be aware of the specific client platform being targeted. Network-based exploitation means that the attack can be conducted from any location with network access to the target client, without requiring physical access or authentication credentials. This makes the vulnerability particularly concerning for enterprise environments where backup systems are critical infrastructure components that must remain operational.
Mitigation strategies for this vulnerability should focus on immediate patching of affected UrBackup installations to version 2.2.7 or later, which contains the necessary fixes for the assertion failure. Network segmentation and firewall rules should be implemented to restrict unnecessary access to backup client ports, limiting the attack surface. Additionally, administrators should implement monitoring solutions to detect unusual client shutdown patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and error handling in network services, aligning with ATT&CK technique T1499.004 which covers network disruption attacks. Organizations should also consider implementing intrusion detection systems that can identify malformed network requests targeting backup services. Regular security assessments and penetration testing of backup infrastructure should be conducted to identify similar vulnerabilities in other network services that may be exposed to similar attack vectors.