CVE-2020-12418 in Firefox
Summary
by MITRE
Manipulating individual parts of a URL object could have caused an out-of-bounds read, leaking process memory to malicious JavaScript. This vulnerability affects Firefox ESR < 68.10, Firefox < 78, and Thunderbird < 68.10.0.
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Analysis
by VulDB Data Team • 05/05/2025
This vulnerability represents a critical memory safety issue in Mozilla's Firefox browser and Thunderbird email client that stems from improper handling of URL object manipulation. The flaw exists in the way these applications process and validate individual components of URL objects, creating a condition where malicious JavaScript code can exploit a buffer overflow scenario through carefully crafted URL parameters. The vulnerability specifically impacts versions prior to the security patches released in Firefox ESR 68.10, Firefox 78, and Thunderbird 68.10.0, indicating a widespread exposure across multiple product lines that rely on the same underlying web engine architecture.
The technical implementation of this vulnerability involves an out-of-bounds read condition that occurs when JavaScript code manipulates specific parts of URL objects, particularly during the parsing or validation process. When an attacker crafts a malicious URL with manipulated components, the browser's internal memory management system fails to properly bounds-check array accesses, allowing the execution of malicious code to read beyond allocated memory boundaries. This memory leakage exposes sensitive process memory contents to the malicious JavaScript context, potentially revealing cryptographic keys, session tokens, or other confidential information stored in memory. The vulnerability operates at the intersection of web platform security and memory safety, where improper input validation leads to information disclosure through memory access violations.
The operational impact of this vulnerability is significant as it enables attackers to perform information disclosure attacks that could lead to privilege escalation or credential theft. An attacker could leverage this vulnerability to extract sensitive data from the browser process memory, potentially compromising user sessions, stored passwords, or cryptographic material. The attack vector requires only the ability to execute malicious JavaScript within the browser context, making it particularly dangerous in environments where users might encounter phishing sites or compromised web content. This vulnerability aligns with attack patterns documented in the attack tree framework where memory corruption issues serve as entry points for more sophisticated exploitation techniques. The affected products' widespread use across enterprise and consumer environments amplifies the potential impact, as a successful exploitation could compromise numerous user systems simultaneously.
Mitigation strategies for this vulnerability focus on immediate version updates to patched releases, which contain proper bounds-checking mechanisms and memory validation routines. Organizations should prioritize rolling out updates to Firefox ESR 68.10, Firefox 78, and Thunderbird 68.10.0 across all affected systems. Additionally, browser security configurations should be reviewed to implement additional protective measures such as strict content security policies and sandboxing controls. The vulnerability demonstrates the importance of robust input validation and memory safety practices in web browser implementations, aligning with security standards such as those outlined in CWE-129 and CWE-131 that address improper bounds checking and buffer overflow conditions. Network administrators should also monitor for suspicious URL patterns and implement web filtering solutions that can detect and block known malicious URL structures. Regular security assessments of browser configurations and user education on avoiding untrusted web content remain essential defensive measures against this class of vulnerability.