CVE-2020-18898 in Exiv2
Summary
by MITRE • 08/20/2021
A stack exhaustion issue in the printIFDStructure function of Exiv2 0.27 allows remote attackers to cause a denial of service (DOS) via a crafted file.
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Analysis
by VulDB Data Team • 08/25/2021
The vulnerability identified as CVE-2020-18898 represents a critical stack exhaustion flaw within the Exiv2 image metadata processing library version 0.27. This issue manifests specifically within the printIFDStructure function, which is responsible for parsing and displaying image file directory structures in various image formats including jpeg and tiff. The flaw enables remote attackers to craft malicious image files that trigger excessive stack memory consumption during the parsing process, ultimately leading to a denial of service condition that can crash applications utilizing Exiv2 for metadata handling.
The technical root cause of this vulnerability stems from inadequate input validation and recursive processing within the printIFDStructure function. When processing specially crafted image files, the function can enter into deeply nested recursive calls that consume stack space exponentially. This recursive behavior is exacerbated by the lack of stack depth limits or recursion counters, allowing attackers to craft files that can cause the stack to overflow and crash the target application. The vulnerability falls under the category of CWE-674, which specifically addresses Uncontrolled Recursion, and represents a classic example of a stack-based buffer overflow scenario that can be exploited for denial of service attacks.
The operational impact of CVE-2020-18898 extends beyond simple service disruption, as it can affect any application or system that relies on Exiv2 for image metadata processing. This includes web applications, content management systems, image processing pipelines, and security tools that handle user-uploaded images. Attackers can exploit this vulnerability by simply uploading or providing access to a maliciously crafted image file, making it particularly dangerous in environments where users can upload content. The vulnerability is particularly concerning in web applications that process images without proper input sanitization, as it allows for remote code execution in some scenarios or at minimum reliable service disruption.
Mitigation strategies for this vulnerability involve multiple layers of protection and system hardening approaches. The most immediate and effective solution is to upgrade to Exiv2 version 0.27.1 or later, which includes patches specifically addressing the stack exhaustion issue through recursive call limiting and improved input validation. Additionally, implementing proper input sanitization and file validation mechanisms can help prevent malicious files from reaching the vulnerable parsing functions. Network-level protections such as rate limiting and file type validation can also provide additional defense in depth. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service through resource exhaustion, and organizations should consider implementing monitoring for unusual stack memory usage patterns to detect potential exploitation attempts.