CVE-2026-101099 in ag-ui
Summary
by MITRE • 09/28/2026
A vulnerability was detected in ag-ui-protocol ag-ui up to 2026-09-23. This affects an unknown part of the file SseParser.kt of the component Kotlin Community SDK. Performing a manipulation results in handling of exceptional conditions. The attack may be initiated remotely. The pull request to fix this issue awaits acceptance.
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Analysis
by VulDB Data Team • 09/28/2026
The ag-ui-protocol library, specifically within versions up to 2026-09-23, contains a vulnerability located in the SseParser.kt file of the Kotlin Community SDK component. This software is designed to parse Server-Sent Events (SSE), a standard protocol for pushing real-time updates from servers to clients over HTTP connections. The identified flaw resides within the logic responsible for handling exceptional conditions during the parsing process, indicating that the code does not properly validate or sanitize input data before processing it through the SSE parser. This lack of robust error handling and input validation creates an opening for remote attackers to exploit the system by sending specially crafted malicious payloads that trigger unhandled exceptions or unexpected behavior within the application runtime environment.
From a technical perspective, this vulnerability aligns with CWE-20 Improper Input Validation and potentially CWE-754: Incorrect Check for Unusual or Exceptional Conditions. When an attacker manipulates the input stream sent to the SseParser.kt module, they can cause the parser to enter states that are not gracefully managed by the surrounding application logic. In many cases, such improper handling of exceptional conditions leads to denial-of-service scenarios where the service crashes or becomes unresponsive due to unrecovered exceptions. Furthermore, depending on how these exceptions propagate through the stack trace and interact with memory management in the Kotlin runtime, there is a potential risk for more severe outcomes such as information disclosure if error messages leak sensitive internal details, or even remote code execution if the exception handling mechanism inadvertently triggers unsafe operations like deserialization of untrusted data.
The operational impact of this vulnerability allows for remote initiation by an attacker who has network access to the affected service. Since SSE is commonly used in web applications and APIs that require real-time notifications, such as chat systems, live dashboards, or financial tickers, a successful exploit could disrupt critical business functions. An adversary could perform a denial-of-service attack against these services, causing downtime for end-users who rely on continuous data streams. Additionally, if the vulnerability leads to application crashes without proper logging or monitoring integration, it may obscure other malicious activities occurring simultaneously, thereby reducing the effectiveness of security monitoring and incident response efforts. The fact that the pull request to fix this issue is still awaiting acceptance means that systems relying on these vulnerable versions remain exposed until a patched version is officially released and deployed by maintainers and users alike.
To mitigate the risks associated with this vulnerability, organizations should monitor for official updates from the Kotlin Community SDK maintainers and apply patches as soon as they become available in subsequent releases of ag-ui-protocol. In the interim, defensive measures include implementing strict input validation at network ingress points using web application firewalls to filter out malformed SSE payloads before they reach the vulnerable parser logic. Developers should also ensure that their applications implement comprehensive exception handling strategies that do not expose stack traces or internal state information to external clients in error responses. Regular security assessments and code reviews focusing on parsing libraries are recommended to identify similar patterns of improper input validation across other components within the software supply chain, ensuring resilience against evolving remote exploitation techniques.