CVE-2017-7772 in Firefox
Summary
by MITRE
Heap-based Buffer Overflow in Graphite2 library in Firefox before 54 in lz4::decompress function.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 05/29/2020
The vulnerability CVE-2017-7772 represents a critical heap-based buffer overflow affecting the Graphite2 library within Mozilla Firefox browsers prior to version 54. This issue specifically manifests within the lz4::decompress function, which is responsible for decompressing data using the LZ4 compression algorithm. The flaw arises when the library processes malformed or specially crafted compressed data streams that exceed the allocated buffer boundaries during decompression operations. The vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions where insufficient boundary checking allows attackers to write beyond allocated memory regions.
The technical exploitation of this vulnerability occurs when Firefox encounters compressed content that triggers the problematic lz4::decompress function in the Graphite2 library. During decompression, the function fails to properly validate input data lengths against allocated buffer sizes, creating opportunities for attackers to craft malicious compressed data that overflows heap memory allocations. This overflow can potentially be leveraged to execute arbitrary code within the browser context, as attackers can manipulate memory layout and overwrite critical data structures or function pointers. The vulnerability is particularly concerning because it operates within the browser's rendering pipeline where compressed font data is commonly processed, making it accessible through various web content delivery mechanisms.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a significant escalation path for attackers seeking to compromise Firefox users. The attack surface includes any web content that utilizes compressed font data, which is increasingly common in modern web applications. Security researchers have noted that this vulnerability can be triggered through crafted web pages, email attachments, or other vector that delivers compressed font resources to the affected browser versions. The potential for remote code execution makes this a high-severity issue that could enable attackers to establish persistent access, steal sensitive information, or deploy additional malware payloads on compromised systems.
Mitigation strategies for CVE-2017-7772 primarily focus on immediate browser updates to version 54 or later, which includes patches that address the buffer overflow in the Graphite2 library's lz4::decompress function. Organizations should implement comprehensive patch management processes to ensure all affected Firefox installations are updated promptly. Additional protective measures include deploying web application firewalls that can detect and block suspicious compressed data patterns, implementing content security policies to restrict font loading from untrusted sources, and utilizing sandboxing mechanisms that limit the potential damage from successful exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007 for command and control through browser-based attacks, making it particularly relevant for enterprise security monitoring and incident response protocols.