CVE-2018-5097 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur during XSL transformations when the source document for the transformation is manipulated by script content during the transformation. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.6, Firefox ESR < 52.6, and Firefox < 58.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2018-5097 represents a critical use-after-free condition that manifests during XSLT (Extensible Stylesheet Language Transformations) processing within Mozilla Firefox and Thunderbird applications. This flaw occurs when script content embedded within the source document manipulates the document structure during transformation operations, creating a scenario where memory previously freed by the application is accessed again. The technical nature of this vulnerability places it firmly within the domain of memory safety issues, specifically categorized under CWE-416 which addresses use-after-free conditions. The vulnerability demonstrates how dynamic content manipulation during processing can lead to memory corruption that adversaries might exploit to execute arbitrary code.
The operational impact of this vulnerability extends across multiple Mozilla products including Firefox ESR versions prior to 52.6, Firefox versions before 58, and Thunderbird versions below 52.6. Attackers can leverage this flaw by crafting malicious XSLT documents that contain embedded scripts designed to manipulate the transformation process in such a way that triggers the use-after-free condition. When the application processes these documents, the memory management system frees certain memory regions while script content continues to reference them, leading to potential crashes or more severe exploitation opportunities. This vulnerability particularly affects web browsing and email applications where users might encounter malformed or malicious content during normal operations.
Security researchers have classified this vulnerability as highly dangerous due to its potential for remote code execution when successfully exploited. The ATT&CK framework categorizes this type of vulnerability under software exploitation techniques, specifically targeting memory corruption flaws that can be leveraged to bypass security protections. The vulnerability's exploitation requires a specific sequence of conditions including the presence of XSLT processing capabilities, script execution within the transformation context, and memory management flaws that allow for the reuse of freed memory. Organizations using affected versions of Firefox or Thunderbird face significant risk as this vulnerability can be triggered through web content or email attachments containing malicious XSLT content. The recommended mitigation strategy involves immediate deployment of security patches provided by Mozilla, which address the memory management issues in XSLT processing and prevent the exploitation of the use-after-free condition. Additionally, administrators should consider implementing content filtering measures and user education to reduce exposure to potentially malicious XSLT content in email and web browsing scenarios.