CVE-2026-50628: Apache CXF Auth Bypass Vulnerability

CVE-2026-50628 Overview

CVE-2026-50628 affects Apache CXF, an open source services framework used to build web services with protocols such as SOAP, REST, and XML/HTTP. A logic error in the OAuthRequestFilter component reverses the intended IP-based access control. The filter rejects legitimate requests from the bound IP address while allowing requests from any other IP address. Operators who enable this security feature inadvertently create an inverse security check, exposing OAuth-protected endpoints to unauthorized network clients. The flaw is tracked under [CWE-20] Improper Input Validation. Apache has released fixed versions 4.2.2 and 4.1.7.

Critical Impact
Network-reachable attackers can bypass the OAuth IP binding control and access protected resources without authentication, leading to full compromise of confidentiality, integrity, and availability.

Affected Products

Apache CXF versions prior to 4.2.2 (4.2.x branch)
Apache CXF versions prior to 4.1.7 (4.1.x branch)
Applications using OAuthRequestFilter with IP binding enabled

Discovery Timeline

2026-06-12 - CVE-2026-50628 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-50628

Vulnerability Analysis

Apache CXF provides OAuthRequestFilter to enforce OAuth-based access control on incoming service requests. The filter supports an IP binding feature that ties an issued OAuth token to the client IP address recorded at token issuance. The intent is to reject any request whose source IP does not match the bound address.

The implementation inverts this comparison. Requests originating from the bound IP are rejected, while requests from any other IP address pass the check. Enabling the feature therefore weakens security rather than strengthening it. Any network attacker that obtains or replays a token can use it from an IP address different from the one bound at issuance.

The vulnerability requires no authentication beyond a valid OAuth token and no user interaction. Exploitation occurs over the network against any CXF endpoint that uses the affected filter configuration.

Root Cause

The defect is a logic error in the conditional branch that compares the request source IP against the token-bound IP. The branch returns the opposite boolean value, causing the filter to treat matching IPs as unauthorized and non-matching IPs as authorized. The issue is categorized under [CWE-20] Improper Input Validation.

Attack Vector

An attacker on the network sends a request carrying a valid OAuth token to a CXF service that has OAuthRequestFilter IP binding enabled. Because the attacker's source IP does not match the bound IP, the filter accepts the request and the service processes it. The legitimate token holder, operating from the bound IP, is denied. Refer to the Apache Security Discussion and the Openwall OSS Security Update for vendor analysis.

No public proof-of-concept code is available at this time, and no verified exploitation code can be provided.

Detection Methods for CVE-2026-50628

Indicators of Compromise

OAuth-authenticated requests to CXF services originating from IP addresses that do not match the token issuance IP recorded in application logs.
Legitimate users reporting 401/403 denials from the bound IP while the same token succeeds from elsewhere.
Unexpected access to OAuth-protected resources from cloud egress IPs, VPN exit nodes, or proxy infrastructure.

Detection Strategies

Inventory all Apache CXF deployments and identify services that load org.apache.cxf.rs.security.oauth2.filters.OAuthRequestFilter with IP binding enabled.
Compare OAuth token issuance IPs against subsequent request source IPs in application and access logs to identify mismatches that succeeded.
Add Web Application Firewall or reverse proxy rules that log the client IP and OAuth token identifier for every protected request.

Monitoring Recommendations

Forward CXF application logs and HTTP access logs to a centralized analytics platform for correlation between token IDs and source IPs.
Alert on OAuth tokens used from more than one source IP within a short interval.
Track failure-to-success patterns where the same token alternates between denied and allowed states.

How to Mitigate CVE-2026-50628

Immediate Actions Required

Upgrade Apache CXF to version 4.2.2 or 4.1.7 immediately.
If patching is delayed, disable IP binding in OAuthRequestFilter until the upgrade is complete, since the feature actively weakens security.
Revoke and reissue OAuth tokens that were issued while the inverse check was active.

Patch Information

Apache has released fixed builds in versions 4.2.2 and 4.1.7. Both releases correct the comparison logic in OAuthRequestFilter so that only requests from the bound IP are permitted. Consult the Apache Security Discussion for release notes and upgrade guidance.

Workarounds

Disable the IP binding feature in OAuthRequestFilter configuration until the patched version is deployed.
Enforce source IP restrictions at a network layer such as a reverse proxy, API gateway, or firewall rather than relying on the affected filter.
Shorten OAuth token lifetimes and require token rotation to limit the window in which a leaked token can be abused.

bash

# Maven dependency update example
# Replace existing cxf-rt-rs-security-oauth2 dependency with a fixed version
mvn versions:set-property -Dproperty=cxf.version -DnewVersion=4.2.2
mvn versions:set-property -Dproperty=cxf.version -DnewVersion=4.1.7