CVE-2017-5446 in Firefox
Summary
by MITRE
An out-of-bounds read when an HTTP/2 connection to a servers sends "DATA" frames with incorrect data content. This leads to a potentially exploitable crash. 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-2017-5446 represents a critical out-of-bounds read condition that manifests within the HTTP/2 protocol implementation of several Mozilla-based applications. This flaw occurs specifically when processing DATA frames sent by servers during HTTP/2 connections, creating a scenario where the application attempts to access memory locations beyond the bounds of allocated buffers. The vulnerability stems from inadequate validation of data content within HTTP/2 frames, allowing maliciously crafted server responses to trigger memory access violations that can result in application crashes or potentially more severe exploitation outcomes.
The technical implementation of this vulnerability resides in the HTTP/2 frame parsing logic where the application fails to properly validate the length and content of DATA frames received from remote servers. When a server sends DATA frames containing malformed or unexpected data content, the receiving application's parser does not adequately check buffer boundaries before attempting to read the frame data. This parsing deficiency creates an opportunity for attackers to craft specific HTTP/2 responses that cause the application to read beyond allocated memory regions, leading to memory corruption and subsequent application instability. The vulnerability is classified under CWE-125 as an out-of-bounds read, which directly maps to the fundamental memory safety issue where applications access memory beyond its allocated boundaries.
The operational impact of CVE-2017-5446 extends across multiple Mozilla products including Thunderbird versions prior to 52.1, Firefox Extended Support Release versions before 45.9 and 52.1, and Firefox versions before 53. This widespread affected scope demonstrates the critical nature of the vulnerability, as it impacts both regular browser releases and extended support versions that many organizations rely upon for stability and security. The crash potential associated with this vulnerability can be leveraged by attackers to perform denial-of-service attacks against targeted users or systems, potentially disrupting legitimate browser functionality and user experience. In certain scenarios, the memory corruption could potentially be exploited to execute arbitrary code, though the primary risk remains application instability and service disruption.
Organizations and users affected by this vulnerability should immediately implement mitigations including updating to the patched versions of their respective software applications. The affected versions represent a significant security risk that can be exploited through man-in-the-middle attacks where malicious actors intercept HTTP/2 traffic and craft malicious responses to trigger the vulnerability. Security teams should prioritize patch deployment across all affected systems, particularly in environments where users may encounter untrusted web content or where HTTP/2 connections are prevalent. Additionally, network administrators can implement monitoring solutions to detect unusual HTTP/2 traffic patterns that might indicate exploitation attempts, while security frameworks such as those aligned with ATT&CK technique T1190 should be employed to identify and respond to potential exploitation of this memory corruption vulnerability. The vulnerability highlights the importance of proper input validation and memory safety practices in network protocol implementations, emphasizing the need for comprehensive testing of edge cases in protocol parsers.