a2aproject a2a-java 1.2.0/1.3.0 Push Notification InMemoryPushNotificationConfigStore.setInfo dns rebinding

Summaryinfo

A vulnerability was found in a2aproject a2a-java. It has been rated as problematic. This vulnerability affects the function InMemoryPushNotificationConfigStore.setInfo of the component Push Notification. This manipulation causes dns rebinding. This vulnerability is handled as CVE-2026-111761. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic was found in a2aproject a2a-java. Affected by this vulnerability is the function InMemoryPushNotificationConfigStore.setInfo of the component Push Notification. The manipulation with an unknown input leads to a dns rebinding vulnerability. The CWE definition for the vulnerability is CWE-350. The product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname. As an impact it is known to affect integrity. The summary by CVE is:

A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Prior to 1.3.0.Final, BasePushNotificationSender in server-common sends task data to the URL in TaskPushNotificationConfig without destination validation, scheme restrictions, or bounds on redirects. InMemoryPushNotificationConfigStore.setInfo stores the URL verbatim, and onCreateTaskPushNotificationConfig does not validate the destination. In the default deployment with push notifications enabled, an unauthenticated caller can register a destination through an inline SendMessage configuration or CreateTaskPushNotificationConfig for an existing task, causing task status and artifact updates to send requests from the server's network position to loopback, private, link-local cloud-metadata, IPv6 unique-local, unspecified, or multicast destinations where routing permits. JdkA2AHttpClient and VertxA2AHttpClient follow redirects, allowing a webhook redirect to bypass creation-time destination checks and convert a POST into a GET; hostname-only checks also do not prevent DNS rebinding. Direct POST delivery can push attacker-influenced task data into internal services, whereas a redirected POST-to-GET request drops the body. The sender discards the fetched response and does not expose delivery success or failure, so the demonstrated behavior does not provide response read-back. No credentials or user interaction are required. This issue is fixed in version 1.3.0.Final.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-111761 since 10/16/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1583.002 for this issue.

Upgrading to version 1.3.0.Final eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-105043). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Programming Language Software

Vendor

• a2aproject

Name

• a2a-java

Version

• 1.2.0
• 1.3.0

Website

• Product: https://github.com/a2aproject/a2a-java/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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