CVE-2017-5444 in Firefox
Summary
by MITRE
A buffer overflow vulnerability while parsing "application/http-index-format" format content when the header contains improperly formatted data. This allows for an out-of-bounds read of data from memory. This vulnerability affects Thunderbird < 52.1, Firefox ESR < 45.9, Firefox ESR < 52.1, and Firefox < 53.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2017-5444 represents a critical buffer overflow flaw in Mozilla's web browser and email client implementations that specifically targets the parsing of "application/http-index-format" content types. This vulnerability manifests when the system encounters header data that does not conform to expected formatting standards, creating conditions where memory access violations can occur. The flaw exists within the core parsing mechanisms responsible for handling HTTP index format data, which is typically used for representing directory listings and web content structures. The issue affects multiple Mozilla products including Thunderbird email client and various Firefox versions, demonstrating the widespread impact of this parsing vulnerability across the browser ecosystem. The vulnerability's classification as a buffer overflow aligns with CWE-121, which describes conditions where insufficient bounds checking allows for memory access beyond allocated buffers, making it particularly dangerous for exploitation.
The technical execution of this vulnerability relies on the improper handling of malformed HTTP header data during the parsing of http-index-format content. When the application encounters header information that deviates from expected formatting conventions, the parsing routine fails to properly validate buffer boundaries, leading to out-of-bounds memory reads. This type of vulnerability falls under the ATT&CK technique T1059.007, which covers the execution of malicious code through input validation flaws, and represents a classic example of how malformed data processing can lead to memory corruption. The flaw specifically impacts the HTTP index format parser, which is designed to handle structured web content but fails when presented with unexpected data patterns, creating opportunities for attackers to read sensitive memory contents without proper authorization. The vulnerability's exploitation potential is heightened because it operates at the parsing layer where legitimate content processing can be manipulated to trigger the overflow condition.
The operational impact of CVE-2017-5444 extends beyond simple information disclosure, as the out-of-bounds memory reads can potentially expose sensitive data from the application's memory space. Attackers could leverage this vulnerability to extract cryptographic keys, session tokens, or other confidential information stored in adjacent memory locations. The affected versions represent a significant portion of the user base, particularly in enterprise environments where Firefox ESR versions are commonly deployed, making this vulnerability particularly attractive to threat actors seeking persistent access. The vulnerability's presence in both Firefox and Thunderbird implementations indicates that the flaw exists in core networking components that handle web content processing, potentially affecting users in both browsing and email contexts. Organizations using these vulnerable versions face increased risk of data breaches and privilege escalation attacks, as the vulnerability could be chained with other exploits to achieve more severe outcomes.
Mitigation strategies for CVE-2017-5444 primarily focus on immediate version updates to patched releases, with Mozilla releasing updates for all affected products including Firefox 53, Firefox ESR 52.1, Firefox ESR 45.9, and Thunderbird 52.1. System administrators should prioritize deployment of these security patches across all affected systems, particularly in environments where users may encounter untrusted web content or email messages. Additional defensive measures include implementing network-level filtering to block suspicious http-index-format content, configuring application sandboxing to limit potential impact of exploitation, and monitoring for anomalous memory access patterns that might indicate exploitation attempts. The vulnerability's remediation aligns with industry best practices for buffer overflow prevention, emphasizing the importance of proper input validation and bounds checking in network protocol implementations. Security teams should also consider implementing automated patch management systems to ensure rapid deployment of security updates and reduce the window of exposure for known vulnerabilities.