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CVE-918 is a critical Server-Side Request Forgery (SSRF) vulnerability affecting the Maven artifact `org.a2aproject.sdk:a2a-java-sdk-server-common` in versions 1.2.0.Final and prior. The flaw stems from a complete lack of destination validation within the push-notification delivery mechanism (BasePushNotificationSender). When a task is configured with a push notification URL, the server stores and invokes HTTP POST requests to this URI without restricting access to sensitive internal network locations, loopback addresses, or cloud metadata endpoints like 169.254.169.254. Furthermore, because the default HTTP clients automatically follow redirects (such as 302 responses), attackers can easily bypass creation-time URL checks via redirect chains or DNS rebinding. This allows unauthenticated external actors to coerce the server into sending arbitrary requests and payloads deep inside internal enterprise boundaries or cloud provider environments.
DailyCVE Form
Platform: Maven
Version: <= 1.2.0.Final
Vulnerability: SSRF
Severity: High
date: 2026-10-21
Prediction: 2026-11-05
What Undercode Say:
To analyze and test this SSRF vulnerability locally or verify network behavior, security researchers often inspect traffic or test route validation using simple curl probes or listener scripts:
Test local listener binding or check egress filtering
nc -lvnp 8080
Example curl test mimicking webhook redirection chains
curl -i -X POST http://localhost:8080/task -d '{"url":"http://169.254.169.254/latest/meta-data/"}'
Exploit: (Educational Purposes!)
An attacker can exploit this vulnerability by supplying a malicious push-notification configuration containing an internal target or cloud metadata address (e.g., [http://169.254.169.254/latest/meta-data/iam/security-credentials/](http://169.254.169.254/latest/meta-data/iam/security-credentials/)). When the server processes tasks and emits status updates, it issues an unauthenticated HTTP request directly from its internal network position. By leveraging HTTP 302 redirects, an attacker can also turn a POST request into a GET request to query restricted endpoints.
// Conceptual illustration of unvalidated URL storage in push configuration
TaskPushNotificationConfig config = new TaskPushNotificationConfig();
config.setUrl("http://169.254.169.254/latest/meta-data/");
InMemoryPushNotificationConfigStore.setInfo(taskId, config);
Protection:
To mitigate CVE-918, administrators and developers must ensure that applications validate the resolved IP address of every destination and redirect hop at connection time, rather than relying on string-based URL checks.
Reject loopback, RFC1918, link-local, unique-local, multicast, and metadata IP ranges.
Restrict URI schemes strictly to HTTP/HTTPS and cap the maximum number of allowed redirects.
Implement resolve-and-pin mechanisms to prevent DNS rebinding attacks.
Apply strict egress firewall rules at the network layer to block host access to metadata services if application-level patches cannot be immediately applied.
Impact:
The impact of this vulnerability includes unauthorized server-side request forgery leading to internal network reconnaissance, cloud metadata exposure, and arbitrary data injection into internal services that accept POST payloads. Although confidentiality read-back is limited due to the application discarding fetched responses, the ability to drive fully controlled requests from within the trusted network boundary creates significant risk for lateral movement and internal service compromise.
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Sources:
Reported By: github.com
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