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TI-2026-76847 Aliases CVE-2026-111761GHSA-q78c-5jjq-57g8

Server-side request forgery in A2A Java SDK push notifications

Priority HIGH 65CWE-918Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

Summary

The A2A Java SDK before 1.3.0.Final does not validate push notification destination URLs (CWE-918). An unauthenticated remote attacker can register a webhook URL for a task, causing the server to send task updates to internal, loopback or cloud-metadata addresses. The HTTP clients follow redirects, so a redirect can bypass the creation-time destination checks.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00586 48th percentileScored 2026-11-07
Fix Fixed a2a-java (a2aproject): 1.3.0.Finalorg.a2aproject.sdk:a2a-java-sdk-server-common (Maven): 1.3.0.Final

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
a2aprojecta2a-javabefore 1.3.0.Final1.3.0.FinalPatch availableCNA
—org.a2aproject.sdk:a2a-java-sdk-server-common (Maven)before 1.3.0.Final1.3.0.FinalPatch availableGHSA-q78c-5jjq-57g8
  • a2a-java Vendora2aproject Affected before 1.3.0.Final Fixed in 1.3.0.Final Patch available CNA
  • org.a2aproject.sdk:a2a-java-sdk-server-common (Maven) Vendor— Affected before 1.3.0.Final Fixed in 1.3.0.Final Patch available GHSA-q78c-5jjq-57g8

Remediation

Update the Maven package org.a2aproject.sdk:a2a-java-sdk-server-common to version 1.3.0.Final, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA a2a-java (a2aproject) Fixed in 1.3.0.Final
  • Fix · GHSA-q78c-5jjq-57g8 org.a2aproject.sdk:a2a-java-sdk-server-common (Maven) Fixed in 1.3.0.Final Advisory →

Timeline

  1. 2026-10-20 Threatist record created from CVE-2026-111761
  2. 2026-10-21 Alias added: GHSA-q78c-5jjq-57g8
  3. 2026-10-21 Fix available: Maven/org.a2aproject.sdk:[email protected] · GHSA-q78c-5jjq-57g8
  4. 2026-10-21 CVSS score added · GHSA-q78c-5jjq-57g8
  5. 2026-10-21 Weakness changed · GHSA-q78c-5jjq-57g8
  6. 2026-10-21 6 new references · GHSA-q78c-5jjq-57g8
  7. 2026-10-22 Priority changed: MEDIUM → LOW
  8. 2026-10-23 CISA SSVC decision points changed
  9. 2026-10-23 Priority changed: LOW → HIGH

References

Advisory 1

Other 5

  • TI-2026-76905 Android A2A Java SDK forwards API keys across redirects CVSS 3.1HIGH 7.5
  • TI-2026-76904 A2A Java SDK default task store skips authorization on task reads CVSS 3.1HIGH 7.5
  • TI-2026-81183 Resource consumption in a2aproject a2a-go REST SSE handler CVSS 4.0MEDIUM 6.9
  • TI-2026-61722 HTTP response splitting in a2aproject a2a-java CVSS 4.0MEDIUM 6.9
  • TI-2026-81185 Denial of service in a2aproject a2a-go Distributed Manager Cancel CVSS 4.0MEDIUM 6.9
  • TI-2026-80567 Error message leaks sensitive information in a2a-go CreateExecutor CVSS 4.0MEDIUM 6.9
See all 21 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences