CVE-2020-23705 in ffjpeg
Summary
by MITRE • 07/16/2021
A global buffer overflow vulnerability in jfif_encode at jfif.c:701 of ffjpeg through 2020-06-22 allows attackers to cause a Denial of Service (DOS) via a crafted jpeg file.
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Analysis
by VulDB Data Team • 07/19/2021
The vulnerability identified as CVE-2020-23705 represents a critical buffer overflow condition within the ffjpeg library's jfif_encode function located in the jfif.c source file at line 701. This flaw affects all versions of ffjpeg up to and including the 2020-06-22 release, creating a significant security risk for systems that process or validate jpeg image files. The buffer overflow occurs during the encoding process when the software fails to properly validate input data length before writing to a pre-allocated memory buffer, creating an exploitable condition that can be triggered through maliciously crafted jpeg files.
The technical implementation of this vulnerability stems from inadequate bounds checking within the jpeg encoding routine where the jfif_encode function processes image data without sufficient validation of the input parameters. When an attacker provides a specially crafted jpeg file containing malformed data structures, the function attempts to write beyond the allocated buffer boundaries, potentially overwriting adjacent memory regions. This condition manifests as a denial of service attack that can cause the application to crash or become unresponsive, effectively preventing legitimate users from accessing the service or processing valid jpeg files. The vulnerability operates at the memory management level and can be classified under CWE-121 as a stack-based buffer overflow, though the specific implementation suggests heap-based exploitation potential.
From an operational impact perspective, systems utilizing ffjpeg for image processing, conversion, or validation tasks become vulnerable to this denial of service condition. Attackers can exploit the vulnerability by preparing a malicious jpeg file that, when processed by an affected application, triggers the buffer overflow and causes the service to terminate unexpectedly. This creates a persistent availability issue that can be particularly damaging in environments where continuous image processing is required, such as web servers, content management systems, or image processing pipelines. The vulnerability does not appear to enable arbitrary code execution directly, but the resulting denial of service can be leveraged as part of broader attack strategies that aim to disrupt service availability.
The exploitation of this vulnerability aligns with tactics described in the MITRE ATT&CK framework under the T1499.004 sub-technique for Network Denial of Service, where attackers target application-level vulnerabilities to cause service disruption. Organizations that rely on ffjpeg for image handling operations should consider implementing input validation measures and image sanitization protocols as immediate defensive actions. The most effective mitigation strategy involves upgrading to a patched version of ffjpeg that addresses the buffer overflow condition through proper bounds checking and memory management practices. Additionally, implementing proper input validation at the application level and employing sandboxing techniques for image processing can provide layered defense mechanisms against this specific vulnerability while maintaining system availability and integrity.