CVE-2002-1049 in HylaFAX
Summary
by MITRE
Format string vulnerability in HylaFAX faxgetty before 4.1.3 allows remote attackers to cause a denial of service (crash) via the TSI data element.
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Analysis
by VulDB Data Team • 06/09/2018
The vulnerability identified as CVE-2002-1049 represents a format string flaw within the faxgetty component of HylaFAX fax server software versions prior to 4.1.3. This particular vulnerability resides in the handling of TSI data elements during fax communication processing, creating a potential vector for remote exploitation that can result in system instability and service disruption. The flaw manifests when the faxgetty daemon processes incoming fax data containing specially crafted format string sequences in the TSI (Terminal Identifier Information) field, which are then improperly handled by the application's string formatting functions.
The technical nature of this vulnerability stems from improper input validation and unsafe string handling practices within the faxgetty module. When the system encounters TSI data that contains format specifiers such as %s, %d, or other format string elements, the application fails to properly sanitize or escape these inputs before passing them to functions like printf or sprintf. This unsafe processing allows attackers to inject malicious format specifiers that can cause the application to read from arbitrary memory locations or attempt to write data to unintended memory addresses, ultimately leading to program termination or crash conditions. The vulnerability specifically affects the TSI data element which is part of the fax protocol communication and contains information about the calling terminal identifier.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it represents a critical security weakness that can be exploited remotely without authentication requirements. Attackers can leverage this flaw to repeatedly crash the faxgetty service, effectively rendering the fax server unavailable to legitimate users and causing significant operational disruption for organizations relying on fax communication services. The vulnerability's remote exploitability means that malicious actors can target systems from outside the local network, making it particularly dangerous for publicly accessible fax servers or those connected to the internet. This type of vulnerability aligns with CWE-134 which specifically addresses format string vulnerabilities where format strings are constructed from user-controlled data without proper validation or sanitization.
Mitigation strategies for CVE-2002-1049 require immediate patching of affected HylaFAX installations to version 4.1.3 or later, which contains the necessary fixes for proper input validation and format string handling. System administrators should also implement network segmentation to limit access to fax servers and consider deploying intrusion detection systems to monitor for suspicious TSI data patterns. The fix implemented in version 4.1.3 typically involves proper validation of TSI data elements and the use of safe string formatting functions that prevent format specifiers from being interpreted as actual format directives. Organizations should also conduct thorough vulnerability assessments of their fax infrastructure and review other components of their fax server software for similar input validation weaknesses. This vulnerability demonstrates the importance of proper input sanitization and aligns with ATT&CK technique T1499 which covers endpoint denial of service attacks targeting system services and applications.