CVE-2017-7885 in jbig2dec
Summary
by MITRE
Artifex jbig2dec 0.13 has a heap-based buffer over-read leading to denial of service (application crash) or disclosure of sensitive information from process memory, because of an integer overflow in the jbig2_decode_symbol_dict function in jbig2_symbol_dict.c in libjbig2dec.a during operation on a crafted .jb2 file.
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Analysis
by VulDB Data Team • 11/29/2022
The vulnerability CVE-2017-7885 represents a critical heap-based buffer over-read flaw in the jbig2dec library version 0.13, which is widely used for decoding jbig2 formatted images. This issue specifically manifests within the jbig2_decode_symbol_dict function located in the jbig2_symbol_dict.c source file of the libjbig2dec.a library. The flaw arises from an integer overflow condition that occurs when processing specially crafted .jb2 files, creating a scenario where the application attempts to read beyond allocated memory boundaries. The vulnerability is particularly concerning as it can be exploited to trigger either application crashes through denial of service or potentially expose sensitive information from process memory through memory disclosure attacks. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, which specifically addresses issues where array indices are not properly validated before use, leading to buffer overflows and over-read conditions.
The technical exploitation of this vulnerability requires an attacker to craft a malicious .jb2 file that triggers the integer overflow within the jbig2_decode_symbol_dict function. When the vulnerable library processes this crafted file, the overflow causes the program to attempt reading memory locations beyond the intended buffer boundaries. This over-read condition can result in two primary attack vectors: denial of service through application crashes that render the affected system or application unusable, or information disclosure where sensitive data from the process memory space becomes accessible to the attacker. The heap-based nature of the vulnerability indicates that the memory corruption occurs within the heap allocation area, making the exploitation more complex but potentially more impactful as it can lead to arbitrary code execution or data leakage. The vulnerability directly maps to the ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage vulnerabilities in software to execute malicious code or cause system instability.
The operational impact of CVE-2017-7885 extends across numerous applications and systems that rely on the jbig2dec library for image processing, including document management systems, web browsers, and image processing software. This vulnerability affects organizations using software that handles jbig2 formatted images, potentially exposing them to both service disruption and data leakage risks. The integer overflow in the symbol dictionary decoding process creates a scenario where legitimate applications using the library become vulnerable to malicious input, making this a particularly dangerous flaw in environments where untrusted image files are processed. Security teams must consider the widespread adoption of jbig2dec across various platforms and applications when assessing the potential impact of this vulnerability, as the exploitation could affect anything from web applications serving user-uploaded images to enterprise document processing systems. The vulnerability's potential for information disclosure makes it especially concerning for systems handling sensitive data, as attackers could potentially extract confidential information from memory during the processing of malicious files. Organizations should prioritize patching affected systems and implementing input validation measures to prevent exploitation of this vulnerability through crafted jbig2 files.