CVE-2018-5098 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur when form input elements, focus, and selections are manipulated by script content. 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-2018-5098 represents a critical use-after-free condition that manifests within web browser implementations when processing form input elements alongside focus and selection manipulation through script content. This type of memory corruption vulnerability arises from improper handling of object references in the browser's rendering engine, specifically affecting the interaction between JavaScript execution and DOM element management. The flaw occurs when the browser attempts to access memory that has already been freed or reallocated, creating a potential entry point for malicious actors to execute arbitrary code or cause system instability. The vulnerability is particularly concerning because it can be triggered through legitimate web page scripting operations that manipulate form elements, making it difficult to distinguish between benign and malicious usage patterns.
The technical implementation of this vulnerability stems from inadequate memory management within the browser's JavaScript engine and DOM handling components. When form input elements receive focus or selection changes, the browser's internal data structures may be modified in ways that leave objects in a state where their memory addresses are freed but references to those addresses persist. This creates a scenario where subsequent script execution might attempt to access the freed memory location, resulting in undefined behavior that can be exploited for code execution. The flaw is classified under CWE-416 as use-after-free vulnerability, which specifically addresses the access of memory after it has been freed, a common vector for privilege escalation and remote code execution attacks. The vulnerability's exploitation potential is further amplified by the fact that it can be triggered through standard web page interactions without requiring special privileges or user consent.
The operational impact of CVE-2018-5098 extends beyond simple browser crashes to encompass potential remote code execution capabilities that could allow attackers to compromise user systems. This vulnerability affects major browser implementations including Thunderbird email client and Firefox browsers, with versions prior to 52.6 for ESR releases and 58 for standard Firefox releases. The attack surface is broad since form elements are ubiquitous on web pages, and the manipulation of focus and selection states is a common scripting pattern used for user interface enhancement and validation. Security researchers have noted that the crash conditions resulting from this vulnerability can be reliably triggered through crafted web content, making it a prime target for drive-by download attacks or phishing campaigns. The vulnerability's presence in both desktop and email client applications creates multiple attack vectors for threat actors seeking to exploit user systems through web-based delivery mechanisms.
Mitigation strategies for CVE-2018-5098 primarily focus on immediate software updates and patch management to address the underlying memory management flaws in affected browser implementations. Organizations should prioritize updating all affected systems to versions that include memory safety improvements and proper object lifecycle management. Browser vendors have implemented various defensive measures including improved memory sanitization, enhanced garbage collection routines, and additional validation checks for DOM element manipulation operations. The vulnerability's remediation aligns with ATT&CK technique T1059.007 for script-based attacks and T1203 for exploitation of memory corruption vulnerabilities. Additional protective measures include implementing web application firewalls, restricting browser scripting capabilities in enterprise environments, and deploying sandboxing technologies to limit the potential impact of successful exploitation attempts. Regular security assessments and monitoring for anomalous browser behavior can help detect exploitation attempts and provide early warning of potential compromise.