CVE-2026-117503 in a2a-go
Summary
by MITRE • 10/27/2026
A vulnerability was determined in a2aproject a2a-go up to 2.4.0. Impacted is an unknown function of the file a2asrv/rest.go of the component REST SSE handler. This manipulation causes resource consumption. It is possible to initiate the attack remotely. Upgrading to version 2.5.0 is recommended to address this issue. Patch name: ff6035bd21e44bb3ee1bfa547885b8c08327fa01. It is recommended to upgrade the affected component.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in a2aproject a2a-go versions up through 2.4.0 represents a significant resource consumption flaw within the REST Server-Sent Events handler, specifically located in the rest.go file of the server-side components. This issue stems from an improper handling mechanism that allows for excessive or unbounded resource allocation during request processing. The core technical failure lies in how the application manages connections and data streams associated with SSE endpoints, where the system fails to adequately limit or monitor the resources consumed by individual client interactions. This lack of control over resource utilization creates a scenario where malicious actors can exploit the handler's behavior to trigger disproportionate CPU usage, memory exhaustion, or network bandwidth depletion relative to the effort required to initiate the attack.
From an operational perspective, this vulnerability enables remote attackers to execute denial-of-service attacks against systems running the affected software versions. Because the flaw is located in a REST SSE handler, it can be triggered over standard HTTP/S protocols without requiring authentication if the endpoint is publicly accessible or through authenticated sessions if access controls are present but insufficiently restrictive. The ability to initiate this attack remotely makes it particularly dangerous for internet-facing services that rely on Server-Sent Events for real-time data delivery. Attackers can send specific malformed requests or sustain connections in a manner that exhausts server resources, leading to service degradation or complete unavailability for legitimate users. This aligns with the Common Weakness Enumeration category CWE-400, which describes conditions where an application does not properly control the allocation and maintenance of a limited resource, thereby allowing attackers to cause denial-of-service situations.
The attack vector is classified under MITRE ATT&CK technique T1499, specifically Endpoint Denial of Service or Network Denial of Service depending on whether the exhaustion targets local system resources or network infrastructure components. By leveraging this vulnerability, adversaries can disrupt business continuity and compromise the availability pillar of the CIA triad without necessarily needing to exfiltrate data or gain unauthorized access to sensitive information. The impact is primarily focused on service stability rather than confidentiality or integrity, although prolonged outages can indirectly affect trust in the system's reliability.
To mitigate this risk, it is strongly recommended that organizations upgrade a2aproject a2a-go to version 2.5.0 or later immediately upon availability. This release contains specific patches designed to address the resource consumption flaw within the REST SSE handler. The patch identified by commit hash ff6035bd21e44bb3ee1bfa547885b8c08327fa01 implements fixes that likely include improved input validation, stricter connection limits, or enhanced monitoring of resource usage during event stream processing. In addition to upgrading the software component, administrators should implement network-level rate limiting and request throttling for SSE endpoints as a defense-in-depth measure. This helps mitigate potential exploitation attempts by restricting the number of concurrent connections or requests from single IP addresses, thereby reducing the effectiveness of any attempted denial-of-service attacks while waiting for full patch deployment across all affected systems.