CVE-2018-17141 in HylaFAX
Summary
by MITRE
HylaFAX 6.0.6 and HylaFAX+ 5.6.0 allow remote attackers to execute arbitrary code via a dial-in session that provides a FAX page with the JPEG bit enabled, which is mishandled in FaxModem::writeECMData() in the faxd/CopyQuality.c++ file.
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Analysis
by VulDB Data Team • 05/17/2023
The vulnerability identified as CVE-2018-17141 represents a critical remote code execution flaw within the HylaFAX fax server software ecosystem. This issue affects both HylaFAX version 6.0.6 and HylaFAX+ version 5.6.0, making it a widespread concern for organizations relying on these fax management systems. The vulnerability stems from improper handling of fax page data during dial-in sessions, specifically when JPEG bit encoding is enabled, creating a pathway for malicious actors to gain unauthorized system access and execute arbitrary commands.
The technical root cause of this vulnerability lies within the FaxModem::writeECMData() function located in the faxd/CopyQuality.c++ source file. This flaw demonstrates characteristics consistent with buffer overflow vulnerabilities as classified by CWE-121, where insufficient bounds checking allows attackers to manipulate memory layout during fax data processing. When a remote attacker establishes a dial-in session and submits a fax page with JPEG bit enabled, the system fails to properly validate or sanitize the incoming data stream, leading to memory corruption that can be exploited to execute malicious code with the privileges of the fax daemon process.
The operational impact of this vulnerability extends beyond simple remote code execution, as it represents a significant compromise of system integrity and confidentiality. Attackers leveraging this vulnerability can potentially gain full control over the fax server, enabling them to access sensitive documents, modify fax configurations, establish persistent backdoors, or use the compromised system as a launch point for further attacks within the network infrastructure. The vulnerability is particularly dangerous because it requires no authentication for exploitation, making it accessible to anyone with network access to the fax server, thus aligning with ATT&CK technique T1203 for legitimate credentials and T1059 for command and scripting interpreter usage.
Organizations affected by this vulnerability should implement immediate mitigations including applying the vendor-provided patches, restricting network access to fax servers through firewall rules, implementing network segmentation to isolate fax services, and monitoring for suspicious fax activity or unauthorized access attempts. Additional protective measures should include disabling unnecessary fax features such as the JPEG bit encoding when not required, implementing intrusion detection systems to monitor for exploitation attempts, and conducting regular security assessments of fax server configurations. The vulnerability also highlights the importance of proper input validation and memory management practices in telephony and fax server software, emphasizing the need for comprehensive security testing of legacy systems that may not have been designed with modern security threats in mind.