CVE-2015-6776 in Chrome
Summary
by MITRE
The opj_dwt_decode_1* functions in dwt.c in OpenJPEG, as used in PDFium in Google Chrome before 47.0.2526.73, allow remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted JPEG 2000 data that is mishandled during a discrete wavelet transform.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability CVE-2015-6776 represents a critical out-of-bounds array access flaw within the OpenJPEG library's discrete wavelet transform implementation, specifically affecting the opj_dwt_decode_1* functions in dwt.c. This vulnerability manifests when PDFium, the PDF rendering engine used by Google Chrome, processes malformed JPEG 2000 image data. The flaw occurs during the discrete wavelet transform operation which is fundamental to JPEG 2000 compression algorithms, where improper bounds checking leads to memory access violations that can be exploited by remote attackers. The vulnerability is particularly concerning as it exists within a widely deployed component that handles multimedia content processing in web browsers, making it a prime target for exploitation in web-based attacks.
The technical implementation of this vulnerability stems from insufficient input validation and boundary checking within the discrete wavelet transform decoding functions. When processing crafted JPEG 2000 data, the opj_dwt_decode_1* functions fail to properly validate array indices against allocated memory boundaries, leading to out-of-bounds memory access patterns. This type of flaw maps directly to CWE-129, which addresses insufficient bounds checking, and CWE-787, which covers out-of-bounds write operations. The underlying issue occurs during the mathematical operations of the discrete wavelet transform where the algorithm assumes certain data structures and memory layouts that may not hold true for malformed input data. The vulnerability can be leveraged to trigger memory corruption that may result in application crashes or potentially more severe consequences depending on the memory layout and execution context.
From an operational impact perspective, this vulnerability enables remote attackers to execute denial of service attacks against Chrome users by simply delivering maliciously crafted JPEG 2000 images within PDF documents or web pages. The attack surface is extensive given that PDFium is used across multiple platforms and browsers, and JPEG 2000 support is enabled by default in many PDF viewers and web applications. The potential for unspecified other impacts suggests that under certain conditions, this vulnerability might be exploitable for code execution or privilege escalation, though the primary documented impact remains denial of service. The ATT&CK framework categorizes this as a software exploitation technique under the T1203 category, which involves exploiting vulnerabilities in software components to achieve unauthorized system access or disruption.
Mitigation strategies for CVE-2015-6776 primarily involve immediate patching of affected systems, with the most effective solution being the upgrade to Google Chrome version 47.0.2526.73 or later where the vulnerability has been addressed through improved input validation and bounds checking in the OpenJPEG library integration. Organizations should also implement network-based protections such as content filtering and sandboxing mechanisms to limit exposure to potentially malicious JPEG 2000 content. Additionally, regular security assessments of PDF processing components and input validation routines should be conducted to identify similar vulnerabilities in other multimedia processing libraries. The fix implemented in the patched versions typically involves adding comprehensive bounds checking and input validation to ensure that all array accesses remain within allocated memory boundaries during discrete wavelet transform operations. Security teams should also consider implementing monitoring for unusual memory access patterns and out-of-bounds operations that may indicate exploitation attempts against similar vulnerabilities in other components.