CVE-2010-1210 in Firefox
Summary
by MITRE
intl/uconv/util/nsUnicodeDecodeHelper.cpp in Mozilla Firefox before 3.6.7 and Thunderbird before 3.1.1 inserts a U+FFFD sequence into text in certain circumstances involving undefined positions, which might make it easier for remote attackers to conduct cross-site scripting (XSS) attacks via crafted 8-bit text.
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Analysis
by VulDB Data Team • 09/21/2021
The vulnerability described in CVE-2010-1210 represents a critical security flaw in the Unicode decoding mechanisms of Mozilla Firefox and Thunderbird applications. This issue resides within the internationalization and character encoding subsystem, specifically in the nsUnicodeDecodeHelper.cpp file that handles text conversion processes. The flaw manifests when the applications encounter undefined or invalid character positions during text decoding operations, particularly affecting 8-bit text processing scenarios.
The technical implementation of this vulnerability stems from how the application handles malformed or undefined Unicode sequences during text decoding. When Firefox or Thunderbird processes text containing undefined positions, the system inserts a U+FFFD replacement character sequence, commonly known as the replacement character or "blob" character. This character appears as a diamond-shaped symbol with a question mark or similar visual indicator in text displays. The insertion of this specific Unicode sequence creates a potential attack vector because it can be manipulated to alter the interpretation of text content in ways that bypass security mechanisms.
The operational impact of this vulnerability extends significantly into the realm of cross-site scripting attacks, as outlined in the Common Weakness Enumeration catalog under CWE-79. Attackers can craft malicious 8-bit text content that, when processed by the vulnerable applications, results in the insertion of U+FFFD sequences that can be exploited to inject malicious code or manipulate the application's behavior. This occurs because the replacement character insertion mechanism can interfere with security checks, input sanitization, and content rendering processes that applications rely upon to prevent XSS attacks.
The attack scenario involves sending specially crafted text content through various communication channels that Firefox or Thunderbird processes, such as email messages in Thunderbird or web content in Firefox. When these applications decode the text, the undefined position handling causes the insertion of U+FFFD sequences that can be manipulated to create conditions where malicious scripts can be executed or security boundaries can be bypassed. This vulnerability particularly affects web browsers and email clients that process international text, as these applications must handle various character encodings and internationalization scenarios.
Security professionals should note that this vulnerability aligns with several ATT&CK framework techniques related to code injection and privilege escalation. The flaw demonstrates how seemingly benign character encoding issues can create significant security risks when they interact with application security controls. Organizations using affected versions of Firefox or Thunderbird should implement immediate mitigation strategies including updating to patched versions, implementing additional input validation, and monitoring for suspicious text processing activities. The vulnerability also underscores the importance of comprehensive testing for internationalization features and character encoding handling in security-sensitive applications, as these components often receive less scrutiny than core security mechanisms.