CVE-2018-7175 in Xpdf
Summary
by MITRE
An issue was discovered in xpdf 4.00. A NULL pointer dereference in readCodestream allows an attacker to cause denial of service via a JPX image with zero components.
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Analysis
by VulDB Data Team • 03/07/2025
The vulnerability CVE-2018-7175 represents a critical NULL pointer dereference flaw within the xpdf 4.00 document processing library, specifically affecting the JPX image handling component. This issue arises when the software encounters a JPX (JPEG 2000 eXtended) image file containing zero components, which creates a scenario where the application attempts to dereference a null pointer during the codestream reading process. The flaw exists in the image decoding logic that fails to properly validate input parameters before attempting to access memory locations, creating an exploitable condition that can be leveraged by malicious actors.
The technical implementation of this vulnerability stems from inadequate input validation within the JPX image parser, where the software assumes that certain image components will always be present and properly initialized. When processing a JPX image with zero components, the internal data structures remain uninitialized or set to null values, yet the code continues execution without proper null checks. This behavior aligns with CWE-476, which specifically addresses NULL pointer dereference vulnerabilities, and demonstrates how insufficient validation of external input data can lead to arbitrary code execution or system instability. The flaw operates at the boundary between legitimate image processing and malformed input handling, making it particularly insidious as it can be triggered through normal document processing operations.
The operational impact of CVE-2018-7175 extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within document processing environments. When exploited, this vulnerability can cause applications relying on xpdf to crash or become unresponsive, effectively denying service to legitimate users while potentially providing attackers with opportunities to escalate their privileges or execute additional malicious code. The vulnerability is particularly concerning in server environments where automated document processing occurs, as it can be triggered through simple file uploads or document rendering operations. Attackers can craft malicious JPX images with zero components to trigger the NULL pointer dereference, causing system instability and potentially enabling further exploitation techniques that align with ATT&CK technique T1203, which covers legitimate program execution through document processing.
Mitigation strategies for CVE-2018-7175 require immediate implementation of input validation patches and software updates to address the underlying NULL pointer dereference condition. System administrators should prioritize updating to patched versions of xpdf that include proper null checks and input validation for JPX image processing. Additionally, implementing strict file type validation and content filtering mechanisms can help prevent malicious JPX files from reaching the vulnerable processing components. Organizations should also consider deploying sandboxing techniques for document processing and implementing network segmentation to limit the potential impact of exploitation. The vulnerability highlights the importance of robust input validation in multimedia processing libraries and demonstrates how seemingly benign file format parsing can become a critical security concern when proper error handling is absent, making it essential for security teams to regularly audit third-party libraries for similar conditions that could lead to privilege escalation or persistent access violations.