CVE-2017-12924 in libfpx
Summary
by MITRE
CDirVector::GetTable in dirfunc.hxx in libfpx 1.3.1_p6 allows remote attackers to cause a denial of service (divide-by-zero error) via a crafted fpx image.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/10/2019
The vulnerability identified as CVE-2017-12924 resides within the libfpx library version 1.3.1_p6, specifically in the CDirVector::GetTable function located in the dirfunc.hxx file. This flaw represents a classic divide-by-zero error that occurs when processing maliciously crafted fpx image files. The libfpx library serves as a component for handling fax image formats and is commonly integrated into various software applications for fax processing and document management systems. The vulnerability manifests when the library attempts to parse an improperly constructed fpx file, triggering a mathematical operation that results in division by zero, ultimately leading to application termination or system instability.
From a technical perspective, this vulnerability operates as a remote denial of service condition that requires no authentication or specialized privileges to exploit. The flaw occurs during the parsing phase of fpx image files where the CDirVector::GetTable function attempts to perform a division operation using a value that has been manipulated by an attacker. The divide-by-zero error represents a fundamental arithmetic exception that causes the program to crash or behave unpredictably, making it a reliable vector for disrupting service availability. This type of vulnerability is classified under CWE-369 as a divide by zero condition, which falls within the broader category of arithmetic errors that can lead to system instability and denial of service conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect any system that relies on libfpx for fax image processing or document handling. Applications that incorporate this library include fax servers, document management systems, and various enterprise software solutions that process fax communications. Attackers can leverage this vulnerability by simply preparing a malicious fpx image file and presenting it to a vulnerable system, potentially causing widespread service outages across organizations that depend on fax processing capabilities. The remote nature of the attack means that exploitation can occur from any location without requiring physical access to the target system, making it particularly dangerous in networked environments where fax processing is common.
Security practitioners should implement multiple layers of defense to protect against this vulnerability. The primary mitigation strategy involves updating to a patched version of libfpx that addresses the divide-by-zero error in the CDirVector::GetTable function. Additionally, input validation mechanisms should be strengthened to filter out malformed fpx files before they reach the vulnerable library functions. Network segmentation and access controls can help limit the potential impact of exploitation by restricting access to fax processing systems. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion or system instability, and represents a common pattern of arithmetic-based vulnerabilities that can be exploited for service disruption. Organizations should also consider implementing monitoring and alerting systems to detect unusual patterns of fax processing failures that might indicate exploitation attempts.