CVE-2020-12422 in Firefox
Summary
by MITRE
In non-standard configurations, a JPEG image created by JavaScript could have caused an internal variable to overflow, resulting in an out of bounds write, memory corruption, and a potentially exploitable crash. This vulnerability affects Firefox < 78.
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Analysis
by VulDB Data Team • 07/10/2020
This vulnerability resides in the Firefox browser's handling of JPEG image processing within non-standard configurations where JavaScript generates image data. The flaw manifests when JavaScript code creates JPEG images that trigger an internal variable overflow condition, leading to memory corruption through out-of-bounds write operations. The vulnerability specifically impacts Firefox versions prior to 78, representing a critical security risk that could be exploited by malicious actors. The issue stems from inadequate bounds checking in the image processing pipeline where the internal variable responsible for tracking image data dimensions exceeds its allocated memory space, causing subsequent memory corruption that could be leveraged for arbitrary code execution.
The technical implementation of this vulnerability involves the manipulation of JPEG image data through JavaScript APIs that allow for dynamic image creation and modification. When JavaScript generates JPEG images with specific parameters or dimensions, the internal processing logic fails to properly validate the size constraints of image metadata fields. This overflow condition occurs in the image parsing and rendering components where integer overflow leads to improper memory allocation and subsequent buffer overflows. The vulnerability can be triggered through web pages that utilize JavaScript to create malicious JPEG content, potentially exploiting the memory corruption to execute arbitrary code within the browser context. This flaw represents a classic buffer overflow vulnerability that could enable privilege escalation and remote code execution.
The operational impact of CVE-2020-12422 extends beyond simple browser crashes to potentially enable full system compromise through remote exploitation. Attackers could craft malicious web pages that, when loaded in vulnerable Firefox versions, would trigger the overflow condition and allow for code execution with the privileges of the browser process. The vulnerability's exploitation potential aligns with attack patterns described in the attack tree framework, where memory corruption vulnerabilities serve as common entry points for advanced persistent threats. Organizations running affected Firefox versions face significant risk, as this vulnerability could be exploited in the wild through drive-by downloads or compromised websites. The exploitability factor is enhanced by the fact that the vulnerability can be triggered through standard web browsing activities without requiring user interaction beyond visiting a malicious website.
Mitigation strategies for this vulnerability primarily involve immediate patching of Firefox installations to version 78 or later, which contains the necessary fixes for the integer overflow condition in JPEG processing. System administrators should implement comprehensive browser update policies to ensure all users are protected against this and similar vulnerabilities. Additional defensive measures include enabling security features such as address space layout randomization and data execution prevention, which can make exploitation more difficult even if the underlying vulnerability is not patched. Network-level protections such as web application firewalls and content filtering systems can help detect and block malicious JPEG content that might trigger this vulnerability. Organizations should also consider implementing browser hardening configurations that restrict JavaScript capabilities for image processing and disable unnecessary image format support to reduce the attack surface. The vulnerability demonstrates the importance of proper input validation and bounds checking in multimedia processing libraries, aligning with common weakness patterns documented in the CWE database under categories related to integer overflows and buffer overflows.