CVE-2011-3670 in Firefox
Summary
by MITRE
Mozilla Firefox before 3.6.26 and 4.x through 6.0, Thunderbird before 3.1.18 and 5.0 through 6.0, and SeaMonkey before 2.4 do not properly enforce the IPv6 literal address syntax, which allows remote attackers to obtain sensitive information by making XMLHttpRequest calls through a proxy and reading the error messages.
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Analysis
by VulDB Data Team • 03/20/2021
This vulnerability exists in multiple Mozilla applications including Firefox Thunderbird and SeaMonkey versions prior to specific patches. The core issue lies in the improper enforcement of IPv6 literal address syntax validation within the XMLHttpRequest implementation. When applications process network requests through proxies, they fail to correctly validate IPv6 addresses, creating a potential information disclosure channel. Attackers can exploit this weakness by crafting malicious XMLHttpRequest calls that target IPv6 addresses through proxy servers, then analyze the error messages returned by the system to extract sensitive information about the network environment.
The technical flaw stems from insufficient input validation of IPv6 address formats within the web application's networking stack. Standard IPv6 addresses must follow specific syntax rules including proper bracketing of addresses and validation of address components. When applications fail to enforce these rules, they become vulnerable to malformed address processing that can leak internal network information through error responses. This vulnerability specifically affects the handling of IPv6 literal addresses in proxy configurations where the application must parse and validate address formats before establishing connections.
The operational impact of this vulnerability allows remote attackers to perform reconnaissance activities without direct network access. By leveraging proxy configurations and carefully crafted XMLHttpRequest calls, attackers can infer information about the target network topology, internal IP address ranges, and potentially even system configurations through the error messages generated during failed address parsing attempts. This information disclosure can significantly aid in planning more sophisticated attacks, including network mapping and target identification for subsequent exploitation phases.
Security professionals should implement immediate mitigations including updating all affected Mozilla applications to their patched versions, which properly enforce IPv6 address syntax validation. Network administrators should also review proxy configurations to ensure proper address validation and consider implementing additional monitoring for unusual XMLHttpRequest patterns. The vulnerability aligns with CWE-20, which addresses improper input validation, and maps to ATT&CK technique T1071.004 for application layer protocol manipulation. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of information disclosure attacks, while maintaining regular patch management processes to address similar vulnerabilities in the future.