CVE-2025-15039: Authentication Bypass Vulnerability

CVE-2025-15039 Overview

CVE-2025-15039 is an authentication bypass vulnerability in the WSO2 Conditional Authentication (Adaptive Authentication) script engine. The flaw allows an attacker to bypass intermediate authentication steps when a specific multi-step pattern involving certain authenticators is configured. Exploitation abuses how the script handles callbacks and re-execution of authentication steps. A successful attacker gains unauthorized access to a targeted user account without completing all required challenges. The issue is tracked as [CWE-693: Protection Mechanism Failure] and disclosed in WSO2 Security Advisory WSO2-2025-4973.

Critical Impact
Attackers can bypass secondary authentication challenges and take over user accounts on affected WSO2 identity products when vulnerable adaptive authentication scripts are in use.

Affected Products

WSO2 products using Conditional Authentication (Adaptive Authentication) scripts with specific event callback configurations
Deployments where the login flow contains an impacted secondary authenticator
Tenants with users enrolled in one of the impacted authenticators

Discovery Timeline

2026-08-06 - CVE-2025-15039 published to NVD
2026-08-06 - Last updated in NVD database

Technical Details for CVE-2025-15039

Vulnerability Analysis

The vulnerability resides in the Conditional Authentication script engine used to orchestrate multi-step login flows. The engine fails to enforce completion state for all mandatory authentication steps when the script re-executes a step through event callbacks. An attacker who completes any preceding authentication steps can trigger the flawed callback path and skip an intermediate challenge. The final authentication decision then treats the flow as fully satisfied, issuing a session for the targeted user. The vulnerability is exploitable over the network without prior privileges or user interaction, and it impacts confidentiality and integrity of user accounts protected by adaptive authentication.

Root Cause

The root cause is a protection mechanism failure [CWE-693] in the state tracking of adaptive authentication scripts. When the script defines particular event callbacks that re-execute an authentication step, the engine does not re-validate that all required steps have reached a completed state. The control-flow logic accepts partial completion as sufficient, breaking the intended step-up authentication contract.

Attack Vector

Exploitation requires four conditions to align: the login flow includes a specific secondary authenticator, the Conditional Authentication script is configured with the vulnerable event callbacks that re-execute a step, the targeted user has one of the impacted authenticators enrolled, and the attacker completes any preceding authentication steps. Under those conditions, the attacker manipulates the authentication callback sequence to skip the intermediate challenge and obtain an authenticated session. See the WSO2 Security Advisory WSO2-2025-4973 for technical specifics.

Detection Methods for CVE-2025-15039

Indicators of Compromise

Authentication audit logs showing successful logins that lack corresponding events for every configured authentication step.
Session establishment events immediately following a partial or truncated adaptive authentication flow.
Repeated authentication attempts from a single source targeting accounts enrolled in impacted secondary authenticators.

Detection Strategies

Correlate WSO2 Identity Server authentication event logs against the expected step sequence defined by each Conditional Authentication script.
Alert on flows where a session token is issued without completion events for all mandatory authenticators.
Review Conditional Authentication scripts for event callbacks that re-execute authentication steps and flag them for inspection.

Monitoring Recommendations

Forward WSO2 Identity Server diagnostic and audit logs to a centralized SIEM for step-by-step flow reconstruction.
Baseline normal step-completion sequences per application and alert on deviations.
Monitor for anomalous account access following authentication events with missing intermediate step records.

How to Mitigate CVE-2025-15039

Immediate Actions Required

Apply the vendor updates and WUM/patch releases referenced in WSO2 Security Advisory WSO2-2025-4973.
Inventory all Conditional Authentication scripts and identify those using event callbacks that re-execute authentication steps.
Force session invalidation and require re-authentication for accounts enrolled in impacted authenticators after patching.

Patch Information

WSO2 has issued patches through its standard update channels. Consult the WSO2 Security Advisory WSO2-2025-4973 for the specific product versions, WUM updates, and remediation steps applicable to your deployment.

Workarounds

Temporarily disable or replace Conditional Authentication scripts that use event callbacks re-executing authentication steps, until patches are applied.
Reduce reliance on the impacted secondary authenticator in login flows where feasible.
Restrict administrative access to authentication script configuration and audit any recent script modifications.

bash

# Configuration example
# Review adaptive authentication scripts under the Identity Server management console
# Path: <IS_HOME>/repository/deployment/server/
# Identify scripts using onSuccess/onFail callbacks that call executeStep() for prior steps
# Replace vulnerable re-execution patterns with linear step sequences until patched