CVE-2001-1497 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 4.0 through 6.0 could allow local users to differentiate between alphanumeric and non-alphanumeric characters used in a password by pressing certain control keys that jump between non-alphanumeric characters, which makes it easier to conduct a brute-force password guessing attack.
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Analysis
by VulDB Data Team • 06/14/2024
This vulnerability exists in Microsoft Internet Explorer versions 4.0 through 6.0 and represents a classic case of information disclosure through user interface behavior analysis. The flaw manifests when users interact with password fields in web forms, where specific control keys cause the browser to navigate between different types of characters. This seemingly innocuous behavior creates a timing-based side channel that reveals information about the password structure to local attackers. The vulnerability is classified under CWE-203, Information Exposure Through Discrepancy, as it exposes password characteristics through observable differences in user interface interaction patterns. Attackers can exploit this by monitoring the specific key combinations that trigger character navigation, thereby distinguishing between alphanumeric and non-alphanumeric characters within a password field.
The technical mechanism behind this vulnerability relies on the browser's handling of keyboard input events and character navigation within password fields. When users press certain control keys such as tab or arrow keys, the browser's internal character traversal logic responds differently to alphanumeric versus non-alphanumeric characters, creating observable differences in the application's behavior. This behavior stems from the way Internet Explorer implemented its password field navigation algorithms, which did not properly abstract the underlying character type distinctions during user interaction. The vulnerability is particularly concerning because it operates at the user interface level rather than at the network or application layer, making it difficult to detect through traditional security monitoring approaches.
The operational impact of this vulnerability significantly weakens password security for users of affected Internet Explorer versions. Attackers can leverage this information to reduce the complexity of brute-force attacks by first identifying the character types present in a password, then focusing their efforts on specific character sets rather than attempting to guess the entire password space. This vulnerability aligns with ATT&CK technique T1212, Exploitation for Credential Access, as it provides a method for attackers to gather credential information through application behavior analysis. The reduced entropy in password guessing attacks can dramatically decrease the time required to compromise user accounts, particularly when combined with other attack vectors or when targeting weak passwords. Security professionals should note that this vulnerability demonstrates how seemingly benign user interface features can create exploitable security weaknesses through side channel analysis.
Mitigation strategies for this vulnerability include updating to newer versions of Internet Explorer where the behavior has been corrected, implementing additional client-side security measures such as character masking or input validation, and employing multi-factor authentication to reduce the impact of credential compromise. Organizations should also consider implementing password policy enforcement that requires stronger passwords and regular rotation to minimize the window of opportunity for attackers exploiting this vulnerability. The vulnerability highlights the importance of considering user interaction patterns and side channel attacks during security design reviews, particularly for applications handling sensitive authentication data. Network security controls such as intrusion detection systems can be configured to monitor for unusual keyboard interaction patterns that might indicate exploitation attempts, though this approach has limitations given the local nature of the vulnerability.