CVE-2019-17005 in Firefox
Summary
by MITRE
The plain text serializer used a fixed-size array for the number of <ol> elements it could process; however it was possible to overflow the static-sized array leading to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.3, Firefox ESR < 68.3, and Firefox < 71.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 01/09/2020
The vulnerability described in CVE-2019-17005 represents a classic buffer overflow condition that emerged within the plain text serialization component of Mozilla's browser and email client applications. This flaw specifically targeted the handling of ordered list elements denoted by the html <ol> tag during the processing of plain text content. The vulnerability stems from the implementation of a fixed-size array that was designed to track the count of ordered list elements encountered during serialization operations. When the system processes content containing an excessive number of <ol> elements, the predetermined array size becomes insufficient to accommodate the actual count, resulting in a memory corruption scenario that can lead to application instability and potential code execution.
The technical nature of this vulnerability aligns with CWE-129, which describes improper validation of array index values, and more specifically with CWE-121, which addresses stack-based buffer overflow conditions. The flaw manifests when the plain text serializer encounters a document structure with more ordered list elements than the statically allocated array can handle, typically exceeding the predefined capacity that was intended to prevent excessive memory consumption. This design limitation creates a scenario where the application's memory management becomes compromised, as the overflow extends beyond the allocated array boundaries and potentially corrupts adjacent memory regions. The vulnerability affects the core serialization logic that converts html content into plain text format, making it particularly dangerous as it can be triggered through normal content processing operations.
The operational impact of this vulnerability extends beyond simple application crashes to encompass potential remote code execution capabilities, particularly when the affected applications process untrusted content from web pages or email messages. Attackers could craft malicious html documents containing an excessive number of nested or sequential <ol> elements to trigger the buffer overflow condition, potentially allowing them to execute arbitrary code on vulnerable systems. The affected versions include Thunderbird versions prior to 68.3, Firefox Extended Support Release versions before 68.3, and standard Firefox versions before 71, representing a significant user base that required immediate patching. This vulnerability particularly impacts users who frequently process web content or email messages containing complex html formatting, as the attack surface expands to include common browsing and email operations.
Mitigation strategies for CVE-2019-17005 primarily focus on immediate software updates to patched versions where the array size limitations have been properly addressed through dynamic memory allocation or more robust bounds checking mechanisms. Organizations should prioritize patching all affected systems and implement additional content filtering measures to prevent processing of suspicious html content. The remediation approach aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as attackers might attempt to leverage this vulnerability to execute malicious code through crafted content. Security teams should also consider implementing network-based intrusion detection systems to monitor for patterns associated with exploitation attempts and maintain comprehensive logging of content processing activities. The vulnerability serves as a reminder of the importance of proper input validation and memory management in preventing buffer overflow conditions that can lead to critical security breaches.