CVE-2018-19876 in Cairo
Summary
by MITRE
cairo 1.16.0, in cairo_ft_apply_variations() in cairo-ft-font.c, would free memory using a free function incompatible with WebKit's fastMalloc, leading to an application crash with a "free(): invalid pointer" error.
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Analysis
by VulDB Data Team • 06/13/2023
The vulnerability identified as CVE-2018-19876 represents a critical memory management issue within the cairo graphics library version 1.16.0. This flaw specifically manifests in the cairo_ft_apply_variations() function located within the cairo-ft-font.c source file, where improper memory deallocation occurs. The issue arises from a fundamental incompatibility between cairo's memory freeing mechanism and WebKit's fastMalloc implementation, creating a dangerous mismatch in memory management protocols that can lead to severe application instability.
The technical root cause of this vulnerability stems from cairo's use of standard free() function calls while operating within environments that employ WebKit's specialized memory allocation system. WebKit's fastMalloc implements its own memory management strategy optimized for web rendering performance, which includes different memory layout patterns and allocation metadata compared to standard system malloc/free implementations. When cairo attempts to free memory that was allocated through WebKit's fastMalloc, the incompatible freeing mechanism causes memory corruption and ultimately results in application crashes with the characteristic "free(): invalid pointer" error message.
This memory management conflict has significant operational impact on applications that rely on both cairo and WebKit components, particularly web browsers and applications using WebKit rendering engines. The vulnerability can be exploited to cause denial of service conditions, where legitimate applications crash unexpectedly during font processing operations. The instability introduced by this flaw can potentially be leveraged by attackers to create more sophisticated exploitation scenarios, as memory corruption vulnerabilities often serve as entry points for more advanced attacks. The vulnerability affects the broader ecosystem of applications that utilize the cairo graphics library for font rendering and text processing, particularly those integrated with web browser components.
Mitigation strategies for CVE-2018-19876 should focus on updating to patched versions of the cairo library where the memory management incompatibility has been resolved. System administrators and developers should prioritize upgrading to cairo versions that address the specific memory deallocation issue in cairo_ft_apply_variations() function. Additionally, implementing proper memory management boundaries between different allocation systems or using memory sanitization tools can help detect and prevent similar issues. The vulnerability aligns with CWE-762, which addresses "Free of Memory not on the Heap," and may be related to ATT&CK technique T1059 for command and scripting interpreter, as exploitation could involve manipulating memory allocation patterns to achieve unauthorized code execution. Organizations should also consider implementing application sandboxing and memory protection mechanisms to reduce the potential impact of such memory corruption vulnerabilities in their deployed systems.