CVE-2026-111761
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.
Does this matter?
Lower severity and a low EPSS score (0.59%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 5.8 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
- EPSS
- 0.59% probability · 48th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-918
- Source
- security-advisories@github.com
EPSS moved from 0.5% on 21 October 2026 to 0.6% on 27 October 2026.
References
- https://github.com/a2aproject/a2a-java/commit/b855b2ae37e4bf23f73e7746ce166fbc5a0b8b5b
- https://github.com/a2aproject/a2a-java/pull/1096
- https://github.com/a2aproject/a2a-java/releases/tag/v1.3.0.Final
- https://github.com/a2aproject/a2a-java/security/advisories/GHSA-q78c-5jjq-57g8
- https://github.com/a2aproject/a2a-java/security/advisories/GHSA-q78c-5jjq-57g8
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.