CVE-2018-7998 in libvips
Summary
by MITRE
In libvips before 8.6.3, a NULL function pointer dereference vulnerability was found in the vips_region_generate function in region.c, which allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted image file. This occurs because of a race condition involving a failed delayed load and other worker threads.
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Analysis
by VulDB Data Team • 02/21/2023
The vulnerability identified as CVE-2018-7998 represents a critical null function pointer dereference flaw within the libvips image processing library version 8.6.2 and earlier. This issue manifests in the vips_region_generate function located in the region.c source file, where a race condition occurs during delayed load operations and concurrent worker thread execution. The flaw enables remote attackers to manipulate image files in such a way that when processed by vulnerable libvips implementations, the software attempts to dereference a null function pointer, resulting in application termination or potentially more severe consequences depending on the execution environment. This vulnerability directly impacts the stability and reliability of applications that depend on libvips for image processing operations, making it particularly dangerous in server environments where image handling is a common task.
The technical exploitation of this vulnerability stems from a race condition scenario that occurs when the delayed loading mechanism fails during concurrent image processing operations. When multiple worker threads attempt to process image regions simultaneously, and one of the delayed load operations fails, the system enters an inconsistent state where function pointers may not be properly initialized. The vips_region_generate function, which is responsible for generating image regions during processing, attempts to call a function pointer that has not been properly set, leading to a null pointer dereference. This race condition typically occurs in multi-threaded environments where the timing of thread execution and resource allocation creates a window where memory management becomes inconsistent, as classified under CWE-362. The vulnerability's classification aligns with ATT&CK technique T1499.004 for network denial of service, as it can be exploited to cause system instability and application crashes.
The operational impact of CVE-2018-7998 extends beyond simple denial of service to potentially enable more sophisticated attack vectors depending on the target environment. When exploited, this vulnerability can cause applications to crash or become unresponsive, effectively rendering image processing functionality unavailable to legitimate users. In web applications that accept user-uploaded images, attackers could craft malicious image files that trigger this vulnerability, leading to service disruption for all users. The vulnerability is particularly concerning in cloud environments and web services where image processing is a core function, as it can be used to perform distributed denial of service attacks against multiple systems simultaneously. The race condition nature of this flaw means that exploitation may not be consistent, but when successful, it can cause cascading failures in systems that depend on image processing capabilities, making it a significant concern for security architects and system administrators.
Mitigation strategies for CVE-2018-7998 primarily focus on upgrading to libvips version 8.6.3 or later, where the race condition has been addressed through improved synchronization mechanisms and proper initialization of function pointers. System administrators should also implement input validation measures to filter potentially malicious image files before they reach the libvips processing pipeline, though this approach may not fully prevent exploitation given the nature of the vulnerability. Additional protective measures include deploying application-level sandboxing techniques, limiting concurrent image processing threads, and implementing proper error handling and recovery mechanisms within applications that utilize libvips. Organizations should also consider monitoring for abnormal application behavior that may indicate exploitation attempts, as the vulnerability can be used to cause persistent service disruption. The fix implemented in libvips 8.6.3 addresses the root cause by ensuring proper thread synchronization during delayed load operations and maintaining consistent function pointer states throughout the processing lifecycle, thereby preventing the race condition that leads to null pointer dereference.