CVE-2025-27935: PingFederate OTP Auth Bypass Vulnerability

CVE-2025-27935 Overview

CVE-2025-27935 affects the OTP Integration Kit for PingFederate. The kit fails to enforce HTTP method validation and state validation on the authentication flow. The server advances the authentication state without verifying the one-time password (OTP), allowing an attacker to bypass multi-factor authentication (MFA).

The weakness is classified under [CWE-306: Missing Authentication for Critical Function]. An authenticated attacker holding valid primary credentials can complete the second factor step without supplying a valid OTP. This collapses the MFA control to a single-factor authentication and exposes downstream applications federated through PingFederate.

Critical Impact
Attackers can bypass OTP-based multi-factor authentication in PingFederate, gaining access to federated applications protected by the OTP Integration Kit.

Affected Products

Ping Identity PingFederate OTP Integration Kit
PingFederate deployments using the OTP Integration Kit as an MFA adapter
Federated applications relying on the OTP Integration Kit for second-factor authentication

Discovery Timeline

2025-12-04 - CVE-2025-27935 published to the National Vulnerability Database (NVD)
2026-04-15 - Last updated in the NVD database

Technical Details for CVE-2025-27935

Vulnerability Analysis

The OTP Integration Kit for PingFederate implements a multi-step authentication flow. After primary credential validation, the user is expected to submit a valid OTP to complete authentication. The integration kit does not enforce HTTP method validation on transitions between authentication states, and it does not adequately validate the authentication state itself.

Because state transitions are not bound to verification of the OTP value, the server progresses to the authenticated state on receipt of a crafted request. The OTP comparison is effectively skipped. The result is an authentication bypass that defeats the second factor entirely.

This is a business logic flaw in the authentication state machine rather than a memory safety or injection issue. It maps directly to [CWE-306] because a critical function — OTP verification — is performed without the required authentication check.

Root Cause

The integration kit advances the session to the "OTP verified" state based on request parameters or sequencing rather than on a cryptographic or server-side check of the submitted OTP. Missing HTTP method validation allows requests using unexpected methods to traverse the flow in ways the developer did not intend. Missing state validation allows the server to accept a transition that should require a verified OTP.

Attack Vector

The attack vector is network-based and requires low privileges, consistent with an attacker who already possesses valid primary credentials, for example through prior phishing or credential reuse. No user interaction is required at the OTP step. The attacker submits an authentication request to the PingFederate endpoint backed by the OTP Integration Kit. By manipulating the HTTP method or the authentication state parameters, the attacker causes the server to mark the OTP factor satisfied. Federated single sign-on (SSO) assertions are then issued, granting access to downstream applications.

No verified proof-of-concept exploitation code is published. See the Ping Identity Security Advisory for vendor technical details.

Detection Methods for CVE-2025-27935

Indicators of Compromise

Successful authentication events in PingFederate audit logs that lack a corresponding OTP verification event for the same session identifier.
HTTP requests to OTP Integration Kit endpoints using unexpected methods (for example, GET where POST is expected) immediately preceding successful authentication.
SSO assertions issued to users whose accounts have not generated OTP delivery events (SMS, email, or TOTP validation) in the same authentication transaction.
Authentication completions occurring faster than the typical OTP entry time observed in baseline telemetry.

Detection Strategies

Correlate PingFederate audit.log entries with OTP delivery and verification subsystem logs to identify sessions that completed without an OTP verification record.
Alert on anomalous HTTP method usage against PingFederate authentication endpoints, particularly any deviation from the documented POST flow.
Hunt for users authenticating from new locations or devices without a matching OTP challenge event in the same time window.

Monitoring Recommendations

Forward PingFederate authentication audit logs to a centralized analytics platform and enforce retention for forensic review.
Establish a baseline for OTP challenge-to-completion ratios per adapter and alert on statistically significant drops.
Monitor federated application access patterns for anomalous post-authentication activity tied to accounts secured by the OTP Integration Kit.

How to Mitigate CVE-2025-27935

Immediate Actions Required

Inventory all PingFederate instances and identify deployments using the OTP Integration Kit.
Apply the fixed version of the OTP Integration Kit published by Ping Identity to every affected deployment.
Force re-authentication of active sessions issued by adapters backed by the OTP Integration Kit after patching.
Review authentication and SSO audit logs from before the patch date for evidence of bypass attempts or unexplained successful authentications.

Patch Information

Ping Identity has published a security advisory and an updated OTP Integration Kit. Refer to the Ping Identity Security Advisory SECADV051 for fixed versions and upgrade guidance. The updated kit is available through the Ping Identity downloads page. Apply the patched integration kit to all PingFederate runtime servers and restart the affected services.

Workarounds

If patching is not immediately possible, disable the OTP Integration Kit adapter and substitute an alternative MFA adapter that is not affected.
Restrict network access to PingFederate authentication endpoints to known corporate ranges and identity proxy gateways while remediation is pending.
Require step-up authentication using an unaffected mechanism (for example, FIDO2 or PingID) for access to sensitive federated applications.
Increase audit logging verbosity on PingFederate and downstream applications to capture bypass attempts during the remediation window.

bash

# Configuration example: verify installed OTP Integration Kit version on a PingFederate server
ls -la $PF_HOME/server/default/deploy | grep -i otp-integration-kit

# Disable the OTP adapter instance in PingFederate (administrative UI path)
# Authentication -> Integration -> IdP Adapters -> [OTP Adapter] -> Deactivate

# Restart PingFederate after deploying the patched kit
$PF_HOME/sbin/pingfederate-shutdown.sh && $PF_HOME/sbin/run.sh