CVE-2026-11538 in WebSphere Application Server
Summary
by MITRE • 09/18/2026
IBM WebSphere Application Server 9.0 and 8.5 is affected by a log injection vulnerability through crafted LTPA token cookies.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/18/2026
The IBM WebSphere Application Server versions 9.0 and 8.5 are susceptible to a Log Injection vulnerability that arises from the improper sanitization of Lightweight Third-Party Authentication tokens, commonly referred to as LTPA tokens. These tokens serve as critical security credentials within the WebSphere ecosystem, facilitating single sign-on capabilities across distributed applications by allowing users to authenticate once and subsequently access multiple resources without re-entering credentials. The vulnerability specifically targets the handling of these tokens when they are transmitted via HTTP cookies during authentication processes or session management operations.
The technical flaw lies in the server's failure to adequately validate or escape special characters within the LTPA token data before it is processed for logging purposes. When a crafted LTPA token containing maliciously constructed input, such as newline characters or other control sequences, is submitted by an attacker, the application server incorporates this raw input directly into its log files without performing necessary sanitization checks. This behavior constitutes a classic instance of CWE-117, Improper Output Neutralization for Logs, where user-controllable data is written to logs in a way that allows attackers to inject arbitrary content into the logging stream.
The operational impact of this vulnerability extends beyond simple data corruption within log files. By injecting crafted sequences, an attacker can manipulate the structure and interpretation of log entries. This manipulation can lead to Log Injection attacks where subsequent parsing tools or security information and event management systems misinterpret the injected lines as legitimate events. Such confusion can obscure genuine malicious activities, making forensic analysis significantly more difficult for system administrators and security operations teams. Furthermore, if the logs are subsequently processed by automated scripts that execute commands based on log content, this vulnerability could potentially escalate into Remote Code Execution scenarios, although the primary risk remains in the integrity of audit trails and monitoring systems.
In addition to disrupting logging mechanisms, successful exploitation can facilitate Log Spoofing attacks as defined under CWE-134. By injecting newline characters followed by forged entries that appear to originate from trusted sources or administrative actions, an attacker can create a false narrative within the logs. This deception allows malicious activities to go undetected for extended periods, thereby compromising the overall security posture of the environment and violating principles of accountability and non-repudiation essential in enterprise IT infrastructures.
To mitigate this vulnerability, IBM has released specific patches and updates that address the input validation logic surrounding LTPA token processing. Administrators should immediately apply the latest fix packs or interim fixes provided by IBM for WebSphere Application Server versions 8.5 and 9.0. These updates implement stricter sanitization routines to ensure that special characters within authentication tokens are properly escaped before being written to log files. In addition to applying vendor patches, organizations should review their logging configurations to enforce strict output encoding standards across all application components. Implementing input validation at the perimeter level through web application firewalls can also provide an additional layer of defense by blocking malformed LTPA tokens before they reach the application server logic. Regular auditing of log files and monitoring for anomalous patterns, such as unexpected line breaks or unusual character sequences in authentication-related logs, remains a critical operational practice to detect potential exploitation attempts early.