HighCVE-2026-111764

A2A Java SDK has a fail-open default task authorization (CVE-2026-111764)

Published 20.10.2026Last modified 20.10.2026Sources: CVE.org, OSV, Hersteller

What is affected, what to do

Update A2aproject A2a-java to version 1.3.0.Final.

Affected: A2aproject A2a-java lt *..1.3.0.Final
Fixed in: A2aproject A2a-java 1.3.0.Final

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

7.5

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

7.5

CVSS v3

Severity High on the scale from 0 to 10.

Source: CVE.org, OSV, Hersteller

0.6 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 48.9

Show all metrics

Severity: High
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 86.64 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 7.5 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 7.5
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.6 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 48.9; High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 20.10.2026
CISA assessment (SSVC): Exploitation: proof of concept · automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 20 October 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-1188, CWE-862

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Draft text for GHSA-qw47-mcm5-934w. The body below drops into the GitHub advisory description field; the metadata block maps to the form fields. Set the patched version at release; publish when the fix ships._

Ecosystem: Maven
Affected package: org.a2aproject.sdk:a2a-java-sdk-server-common (task store / authorization)
Affected versions: <= 1.2.0.Final (and 1.2.1.Final-SNAPSHOT on main prior to the fix)
Patched version: (the release that carries the fix, e.g. 1.2.1.Final)
CWE: CWE-1188 (Insecure Default Initialization), CWE-862 (Missing Authorization)
Severity: High
CVSS v3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (7.5, High)

Details

The default task store performs no authorization on task reads. InMemoryTaskStore's no-arg constructor sets authorizationProvider = null, and InMemoryTaskStore.get(String taskId) is a bare map lookup with no authorization check regardless of provider:

public InMemoryTaskStore() {
    this.authorizationProvider = null;   // default wiring
}

@Override
public @Nullable Task get(String taskId) {
    return tasks.get(taskId);            // no owner / caller check
}

Authorization is enforced only when the application both supplies a TaskAuthorizationProvider and routes requests through AuthorizationRequestHandlerDecorator (via CDI), which checks ownership before delegating. A server that uses the default store, or wires DefaultRequestHandler.builder().build() manually, or integrates through a non-CDI stack (e.g. Spring), never reaches that check. The safe posture is therefore opt-in and the shipped default is the unsafe one. A caller can read a task created by another caller simply by knowing or guessing its id.

Summary

With the SDK's default configuration, task reads are not authorized: any caller can retrieve a task (including its status, context, message history, and artifacts) created by another caller, by supplying the task id.

PoC

Using only the real production classes wired the default way (no mocks):

Construct the default store: InMemoryTaskStore store = new InMemoryTaskStore(); (no-arg constructor, so no authorization provider).
As one caller, save a task: store.save(victimTask, false); with id victim-task-42.
As a second, unrelated caller with no auth context, read it back: store.get("victim-task-42").

The second caller receives the first caller's task in full, with no authorization check:

unauthenticated get(victim-task-42) returned task owned by nobody-checked: victim-task-42 / ctx=victim-ctx

Verified on main (commit 72d220c, JDK 21) and reproduces unchanged on 1.2.0.Final.

Impact

Task data crosses caller boundaries with no authorization. In any multi-caller deployment built on the default wiring, one caller can enumerate and read another caller's tasks, including task status, context id, the message history, and any artifacts the task carries, which for agent workloads is frequently sensitive input and generated content. Because the insecure behaviour is the default rather than a misconfiguration, it is easy to ship unintentionally, and in the default/reference deployment the transport endpoints are served without authentication enforced, so the read is reachable by an unauthenticated caller (PR:N). CVSS is scored against the default configuration as shipped.

Remediation

Fail closed by default: deny task reads when no authorization provider is configured, rather than treating a missing provider as allow-all, and apply the authorization check in the store's get path (not only in list and the CDI decorator) so it holds regardless of how the handler is wired. If the current permissive default is retained for single-user/testing scenarios, emit a prominent startup warning when the server comes up with no authorization provider so it cannot be shipped by accident.

Workarounds

Until a fixed release, configure a TaskAuthorizationProvider and ensure requests are routed through the authorization decorator (CDI wiring), rather than relying on the default no-arg store or a manually built handler.

References

CWE-1188: Insecure Default Initialization of Resource: https://cwe.mitre.org/data/definitions/1188.html
CWE-862: Missing Authorization: https://cwe.mitre.org/data/definitions/862.html

Source: NVD (NIST), OSV (Open Source Vulnerabilities), GitHub Security Advisories, cvelistv5

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
a2aproject	a2a-java	`< 1.3.0.Final`	`1.3.0.Final`
maven	org.a2aproject.sdk:a2a-java-sdk-server-common	`1.0.0.CR1` `—` `< 1.3.0.Final` `1.0.0.Alpha4` `1.1.0.Final` `1.2.0.Final` `1.0.0.Final` `1.0.0.Beta1`	— `1.3.0.Final` `1.3.0.Final` — — — — —

Vendors and products

A2aproject A2a-java

Weakness classes (CWE)

CWE-1188Initialization of a Resource with an Insecure Default
Base
The product initializes or sets a resource with a default that is intended to be changed by the product's installer, administrator, or maintainer, but the default is not secure.
Entry at MITRE CWE-1188
CWE-862Missing Authorization
Class
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Entry at MITRE CWE-862

References & sources

github.coma2aproject/a2a-java/commit/efb4e985e99390c4fc1f78c0a187a4254c0a…x_refsource_MISC, web
github.coma2aproject/a2a-java/pull/1095x_refsource_MISC, web
github.coma2aproject/a2a-java/releases/tag/v1.3.0.Finalx_refsource_MISC, web
github.coma2aproject/a2a-java/security/advisories/GHSA-qw47-mcm5-934wx_refsource_CONFIRM, web
NVD (NIST)vuln/detail/CVE-2026-111764advisory
github.coma2aproject/a2a-javapackage

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

20.10.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: proof of concept, automatable: yes

New references:

https://github.com/a2aproject/a2a-java/security/advisories/GHSA-qw47-mcm5-934w

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/a2aproject/a2a-java/security/advisories/GHSA-qw47-mcm5-934w
SSVC assessment	added	—	{"id":"CVE-2026-111764","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-20T16:15:13.020004Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

20.10.2026ReceivedGitHub

CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Weakness type: CWE-1188, CWE-862

Description added or changed

New references:

Show 9 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	A2A Java SDK is the official Java SDK for the Agent2Agent (A2A) Protocol. Prior to 1.3.0.Final, the default InMemoryTaskStore configuration performs no authorization on task reads: the no-argument constructor sets authorizationProvider to null, and InMemoryTaskStore.get(String taskId) returns the stored task without checking the caller or owner. Authorization depends on supplying a TaskAuthorizationProvider and routing requests through AuthorizationRequestHandlerDecorator, whether installed through CDI or explicitly by the application. Default store wiring and manually constructed DefaultRequestHandler.builder().build() handlers, including integrations such as Spring, leave task reads unprotected when no effective authorization-provider and decorator check is installed. In a multi-caller deployment using the default configuration, a caller who knows or guesses another caller's task ID can retrieve the task status, context ID, message history, and artifacts. The default/reference transport endpoints do not enforce authentication, so the task-read disclosure is reachable by an unauthenticated caller rather than requiring a privileged account. This issue is fixed in version 1.3.0.Final.
CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness type (CWE)	added	—	CWE-1188
Weakness type (CWE)	added	—	CWE-862
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/111xxx/CVE-2026-111764.json">CVE-2026-111764</a>
Reference	added	—	https://github.com/a2aproject/a2a-java/commit/efb4e985e99390c4fc1f78c0a187a4254c0a2553
Reference	added	—	https://github.com/a2aproject/a2a-java/pull/1095
Reference	added	—	https://github.com/a2aproject/a2a-java/releases/tag/v1.3.0.Final
Reference	added	—	https://github.com/a2aproject/a2a-java/security/advisories/GHSA-qw47-mcm5-934w

Source identifier: security-advisories@github.com

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