CVE-2021-37620 in Exiv2
Summary
by MITRE • 08/10/2021
Exiv2 is a command-line utility and C++ library for reading, writing, deleting, and modifying the metadata of image files. An out-of-bounds read was found in Exiv2 versions v0.27.4 and earlier. The out-of-bounds read is triggered when Exiv2 is used to read the metadata of a crafted image file. An attacker could potentially exploit the vulnerability to cause a denial of service, if they can trick the victim into running Exiv2 on a crafted image file. The bug is fixed in version v0.27.5.
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Analysis
by VulDB Data Team • 08/14/2021
The vulnerability identified as CVE-2021-37620 represents a critical out-of-bounds read flaw within the Exiv2 library and command-line utility ecosystem. This security issue affects versions v0.27.4 and earlier, where the software fails to properly validate metadata structures when processing image files. The flaw manifests specifically during the metadata reading process, where Exiv2 attempts to access memory locations beyond the allocated buffer boundaries. The vulnerability stems from inadequate input validation mechanisms that do not sufficiently sanitize or verify the integrity of image file metadata structures before processing them.
The technical exploitation of this vulnerability occurs when a maliciously crafted image file is processed by Exiv2, triggering the out-of-bounds memory access pattern. This type of flaw falls under CWE-129, which specifically addresses insufficient validation of length of input buffers, and more broadly relates to CWE-787, which covers out-of-bounds write or read operations. The vulnerability operates at the intersection of memory safety and input validation, where the software's failure to properly validate metadata field lengths allows for unauthorized memory access patterns. When exploited, this condition can cause the application to crash or behave unpredictably, creating potential denial of service scenarios that could be leveraged by attackers to disrupt services.
From an operational perspective, the impact of CVE-2021-37620 extends beyond simple service disruption to potentially enable more sophisticated attack vectors. The vulnerability's trigger mechanism through crafted image files aligns with ATT&CK technique T1203, which involves exploiting software vulnerabilities to gain system access. The flaw can be particularly dangerous in environments where Exiv2 is used to process untrusted image content, such as web applications, content management systems, or digital asset management platforms. Attackers could craft malicious image files designed to trigger the out-of-bounds read during metadata extraction, potentially leading to application crashes that could be exploited for denial of service attacks or even information disclosure if the memory access patterns reveal sensitive data.
The mitigation strategy for this vulnerability requires immediate deployment of Exiv2 version v0.27.5, which includes the necessary patches to address the out-of-bounds read condition. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected versions of Exiv2, particularly those handling user-uploaded content or processing third-party image files. Security teams should implement input validation controls at multiple layers, including file format validation and metadata sanitization, to reduce the risk of exploitation. Additionally, network segmentation and access controls should be strengthened to limit the potential impact of successful exploitation attempts. The fix addresses the root cause by implementing proper bounds checking and input validation mechanisms that prevent the software from accessing memory beyond the intended buffer boundaries, thereby eliminating the conditions that enable the out-of-bounds read to occur.