CVE-2021-29842 in WebSphere Application Server
Summary
by MITRE • 09/16/2021
IBM WebSphere Application Server 7.0, 8.0, 8.5, 9.0 and Liberty 17.0.0.3 through 21.0.0.9 could allow a remote user to enumerate usernames due to a difference of responses from valid and invalid login attempts. IBM X-Force ID: 205202.
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Analysis
by VulDB Data Team • 09/19/2021
This vulnerability exists within IBM WebSphere Application Server versions 7.0 through 9.0 and Liberty versions 17.0.0.3 through 21.0.0.9, representing a significant authentication weakness that could be exploited by remote attackers to perform user enumeration attacks. The flaw stems from inconsistent response behavior between legitimate and invalid login attempts, creating a timing or response differentiation that reveals whether a specific username exists within the system. This type of vulnerability aligns with CWE-204, which categorizes improper handling of responses that may disclose sensitive information, and falls under the broader category of information disclosure vulnerabilities that can facilitate subsequent attack phases.
The technical mechanism behind this vulnerability involves the application server's authentication mechanism returning different response times or error messages when processing login requests for valid versus invalid usernames. Attackers can exploit this inconsistency by systematically testing various username combinations and analyzing the responses to determine which usernames are valid within the system. This enumeration capability allows threat actors to build comprehensive user lists that can then be used for targeted brute force attacks, credential stuffing, or social engineering campaigns. The vulnerability particularly affects authentication systems that do not implement consistent response handling, creating a side-channel attack vector that bypasses traditional security controls.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with a crucial reconnaissance step that significantly reduces the complexity of subsequent attacks. Once valid usernames are discovered, attackers can focus their efforts on cracking specific accounts rather than attempting to guess user credentials across an entire user base. This vulnerability particularly affects organizations that rely on WebSphere for enterprise applications, as it can expose the entire user directory of applications running on these servers. The attack surface is further expanded because the vulnerability affects multiple major versions of IBM WebSphere, making it a widespread concern for enterprises maintaining legacy systems. According to ATT&CK framework, this vulnerability maps to T1078.004, which covers valid accounts and T1562.001, which covers disabled or removed accounts, as the enumeration process effectively reveals account validity information.
Organizations should implement immediate mitigations including enabling consistent authentication response handling across all authentication endpoints, implementing account lockout mechanisms after failed login attempts, and deploying rate limiting controls to prevent automated enumeration attempts. The IBM security advisory recommends upgrading to patched versions of WebSphere Application Server and Liberty, as these releases contain proper response handling that eliminates the timing differences between valid and invalid authentication attempts. Additional protective measures include implementing intrusion detection systems that can identify unusual authentication patterns, deploying multi-factor authentication to reduce the impact of credential compromise, and conducting regular security assessments to identify similar response inconsistency vulnerabilities in other authentication systems. Network segmentation and access controls should also be strengthened to limit the potential impact of successful enumeration attacks.