CVE-2026-77883: Apache Syncope Information Disclosure Flaw

CVE-2026-77883 Overview

CVE-2026-77883 is an information disclosure vulnerability in Apache Syncope, an open-source identity management system. An administrator with entitlements to manage Derived Schemas can craft a malicious Java Expression Language (JEXL) expression. When another administrator with User read entitlements evaluates that expression, the payload exposes sensitive data from LinkedAccount entities or Manager references, including hashed credentials.

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. Apache has published fixes in versions 4.0.8 and 4.1.3.

Critical Impact
A privileged administrator can weaponize Derived Schema JEXL expressions to exfiltrate hashed credentials belonging to linked accounts and manager users, enabling downstream credential cracking and identity compromise.

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-2026-77883 published to the National Vulnerability Database
2026-09-14 - Apache Software Foundation disclosed the issue on the Apache Mailing List Thread and via the OpenWall OSS Security Update
2026-09-14 - Last updated in the NVD database

Technical Details for CVE-2026-77883

Vulnerability Analysis

Apache Syncope uses Derived Schemas to compute attribute values dynamically from other user attributes. These schemas rely on JEXL, a scripting language that evaluates expressions against a runtime context. The runtime context exposed to Derived Schema evaluation includes references to related objects such as LinkedAccount and Manager entities.

The flaw allows an administrator with Derived Schema management entitlements to author a JEXL expression that traverses these related objects and returns their internal fields. When a second administrator with User read entitlements retrieves the user, the expression executes server-side and returns the derived value, including sensitive fields that should never be projected through Derived Schemas. Hashed credentials returned in this manner can then be extracted for offline cracking.

The weakness is classified under [CWE-202]: Exposure of Sensitive Information Through Data Queries.

Root Cause

The root cause is insufficient filtering of the object graph exposed to JEXL evaluation in Derived Schemas. Syncope did not restrict which fields of LinkedAccount and Manager references could be dereferenced during expression evaluation, so protected attributes including hashed credentials remained reachable.

Attack Vector

Exploitation requires two administrators or one attacker who controls both roles. The attacker first creates or modifies a Derived Schema containing a JEXL expression that reads sensitive fields from linked accounts or manager objects. When any administrator with User read permission reads a user account that resolves the Derived Schema, the expression executes and the sensitive value is returned in the API response. No user interaction is required beyond the normal read operation.

Because no verified proof-of-concept has been published, this article does not include exploit code. Refer to the Apache Mailing List Thread for vendor technical detail.

Detection Methods for CVE-2026-77883

Indicators of Compromise

Newly created or recently modified Derived Schemas whose JEXL expressions reference linkedAccounts, manager, password, or credential-related properties.
Unusual read activity against user accounts that carry LinkedAccounts or defined Managers, especially from administrator accounts that do not normally perform bulk user reads.
Audit log entries showing Derived Schema create or update events immediately followed by user read API calls returning unexpected attribute payloads.

Detection Strategies

Review the SchemaLogic and audit trail for all Derived Schema definitions and flag any expression that dereferences credential fields or nested account objects.
Correlate administrator entitlement changes with subsequent Derived Schema modifications to identify potential abuse of the entitlement model.
Baseline the volume and shape of user read API responses so that responses containing unexpected string fields trigger investigation.

Monitoring Recommendations

Enable Syncope audit logging for SchemaLogic, UserLogic, and AnyObjectLogic operations and forward events to a central SIEM.
Alert on any JEXL expression change performed by administrators outside of an approved change window.
Monitor authentication systems for credential-stuffing or brute-force patterns that could indicate offline cracking of exfiltrated hashes.

How to Mitigate CVE-2026-77883

Immediate Actions Required

Upgrade Apache Syncope to version 4.0.8 or 4.1.3. Deployments on the 3.0.x branch should plan an upgrade path since a fixed 3.0.x release is not listed in the advisory.
Audit all existing Derived Schemas and remove any JEXL expression that references linked account or manager credential fields.
Rotate credentials for any user whose hashed password may have been exposed through a Derived Schema read.

Patch Information

Apache Syncope 4.0.8 and 4.1.3 remove the ability for Derived Schema JEXL expressions to reach sensitive fields on LinkedAccount and Manager references. Details are published in the Apache Mailing List Thread and the OpenWall OSS Security Update.

Workarounds

Restrict the Derived Schema management entitlement to a small set of highly trusted administrators until the upgrade is applied.
Enforce a code-review workflow for any Derived Schema change so that JEXL expressions are inspected before deployment.
Temporarily remove Derived Schemas that are not business-critical to reduce the attack surface.

bash

# Verify installed Syncope version and confirm remediation
curl -s -u admin:<password> https://syncope.example.com/syncope/rest/syncope | jq '.version'

# Expected output after remediation: "4.0.8" or "4.1.3" (or later)