CVE-2026-73370: Apache Syncope Auth Bypass Vulnerability

CVE-2026-73370 Overview

CVE-2026-73370 is an Incorrect Authorization vulnerability [CWE-863] in Apache Syncope. The flaw resides in the Reconciliation service's pull and push operations, where delegated administration security checks are incomplete. Administrators lacking the required entitlements can invoke these operations and manipulate identity data outside their assigned scope.

The issue affects Apache Syncope releases from 3.0.0-M0 through 3.0.16, from 4.0.0-M0 through 4.0.7, and from 4.1.0-M0 through 4.1.2. The Apache Syncope project recommends upgrading to 4.0.8 or 4.1.3 to remediate the vulnerability.

Critical Impact
Delegated administrators can bypass entitlement checks in Reconciliation pull and push calls, gaining unauthorized ability to synchronize or modify identity data across the Syncope deployment.

Affected Products

Apache Syncope 3.0.0-M0 through 3.0.16
Apache Syncope 4.0.0-M0 through 4.0.7
Apache Syncope 4.1.0-M0 through 4.1.2

Discovery Timeline

2026-09-14 - CVE-2026-73370 published to the National Vulnerability Database
2026-09-14 - Apache Software Foundation publishes advisory on the security mailing list
2026-09-14 - Last updated in NVD database

Technical Details for CVE-2026-73370

Vulnerability Analysis

Apache Syncope is an open source identity management system. It supports delegated administration, allowing designated administrators to manage only the users, groups, or realms they are entitled to. The Reconciliation service exposes pull and push operations that synchronize identity data between Syncope and external resources.

The vulnerability stems from incomplete authorization checks in the Reconciliation service. When an administrator calls pull or push, the service does not fully validate whether the caller holds the required entitlements for the targeted resource or realm. As a result, an authenticated administrator with limited delegation scope can trigger reconciliation operations against resources outside their assigned boundary.

Because Reconciliation operations create, update, or delete identity data on connected systems, exploitation can propagate unauthorized changes across downstream applications integrated with Syncope. This undermines the delegated administration model that separates duties between administrators.

Root Cause

The root cause is a missing or incomplete authorization enforcement path in the Reconciliation pull and push handlers. The endpoints accept administrator calls without verifying the full set of entitlements required for the target resource. This is a classic instance of Incorrect Authorization [CWE-863].

Attack Vector

Exploitation requires network access to the Syncope REST API and authenticated credentials for any administrator account that possesses partial delegated entitlements. The attacker issues a Reconciliation pull or push request against a resource outside their entitlement scope. The server processes the request without rejecting it, granting the attacker the effect of holding entitlements they were never assigned.

The vulnerability manifests at the service layer; refer to the Apache Security Mailing List Thread and the OpenWall OSS-Security Discussion for the official advisory language.

Detection Methods for CVE-2026-73370

Indicators of Compromise

Reconciliation pull or push REST calls originating from administrator accounts whose delegated scope does not include the targeted resource or realm.
Unexpected changes to user, group, or any-object records on external resources managed by Syncope, correlated with Reconciliation task executions.
Audit log entries showing Reconciliation task submissions immediately followed by identity data mutations outside the caller's normal administrative boundary.

Detection Strategies

Compare Syncope audit logs against the delegated administrator entitlement matrix and flag Reconciliation calls that target resources outside the caller's authorized scope.
Monitor the Syncope REST API for POST requests to Reconciliation endpoints (/reconciliation/push, /reconciliation/pull) from non-privileged administrator sessions.
Baseline normal Reconciliation task volume per administrator and alert on statistically significant deviations.

Monitoring Recommendations

Forward Syncope application, audit, and REST access logs to a centralized SIEM for correlation with identity provisioning events on downstream resources.
Track authentication and authorization decisions for the Syncope admin console and REST API, retaining sufficient history to reconstruct delegated-administration abuse.
Enable connector-side logging on external resources so unauthorized reconciliation-driven changes can be traced back to the originating Syncope operation.

How to Mitigate CVE-2026-73370

Immediate Actions Required

Upgrade Apache Syncope to version 4.0.8 or 4.1.3, which contain the authorization fix for the Reconciliation service.
Inventory all delegated administrator accounts and review their entitlements, revoking any that are no longer required.
Rotate credentials for administrator accounts that may have been used to invoke Reconciliation operations while vulnerable builds were deployed.
Audit recent Reconciliation task executions and validate downstream identity changes against expected business activity.

Patch Information

The Apache Syncope project has released fixed versions 4.0.8 and 4.1.3. Users on the 3.0.x branch should consult the Apache Security Mailing List Thread for upgrade guidance, because the advisory identifies fixes for the 4.0.x and 4.1.x branches only.

Workarounds

Restrict network access to the Syncope REST API so only trusted management hosts can reach Reconciliation endpoints while the upgrade is scheduled.
Temporarily suspend delegated administrator accounts that are not strictly required, reducing the population of principals that can trigger Reconciliation calls.
Disable or limit the Reconciliation pull and push tasks for non-superuser administrators through operational controls until patched builds are deployed.

bash

# Configuration example
# Restrict access to Syncope Reconciliation endpoints at a reverse proxy
# until upgrading to 4.0.8 or 4.1.3
location ~ ^/syncope/rest/reconciliation/(pull|push) {
    allow 10.0.0.0/24;   # trusted management subnet
    deny  all;
    proxy_pass http://syncope-backend;
}