CVE-2026-35149: HCL DFXServer Auth Bypass Vulnerability

CVE-2026-35149 Overview

CVE-2026-35149 is an authentication bypass vulnerability affecting HCL DFXServer. Attackers exploit the flaw by intercepting and altering the server's authentication responses during the login flow. Manipulating these responses allows an unauthenticated network attacker to gain access to the application without presenting valid credentials. The weakness is categorized as improper authentication [CWE-294], where the client trusts server-supplied verification data that can be tampered with in transit. HCL Software has published guidance in its knowledge base for affected customers.

Critical Impact
An unauthenticated remote attacker can bypass authentication and access HCL DFXServer by modifying authentication responses in transit.

Affected Products

HCL DFXServer (see vendor advisory for specific affected versions)

Discovery Timeline

2026-07-16 - CVE-2026-35149 published to the National Vulnerability Database (NVD)
2026-07-16 - Last updated in the NVD database

Technical Details for CVE-2026-35149

Vulnerability Analysis

CVE-2026-35149 is an authentication bypass in HCL DFXServer caused by the application trusting authentication decisions carried in server responses. An attacker positioned on the network path, or capable of proxying traffic between the client and server, can intercept the response returned during the authentication handshake. By altering the fields that signal authentication success or user identity, the attacker convinces the application that verification has completed. The result is unauthorized access to protected application functionality without ever supplying valid credentials.

The vulnerability is remotely exploitable over the network, requires no privileges, and requires no user interaction. Successful exploitation grants access to confidential data handled by the application and permits limited modification of application state.

Root Cause

The underlying weakness maps to [CWE-294] Authentication Bypass by Capture-replay and improper verification of the authentication result. The client-side logic makes trust decisions based on server-supplied response data without cryptographic binding or integrity protection. Because the response is not authenticated end to end, any actor able to modify traffic between the two endpoints can forge a successful authentication outcome. The design assumes the transport channel is trustworthy, which is not a valid assumption in most deployment scenarios.

Attack Vector

Exploitation requires network access to the authentication traffic between a client and the HCL DFXServer instance. An attacker uses a proxy, a compromised network device, or a machine-in-the-middle position to intercept the server response following an authentication attempt. The attacker rewrites the response to indicate success and forwards it to the client. The application then treats the session as authenticated and grants access. No valid username or password is required. The attacker does not need prior privileges on either endpoint.

No public proof-of-concept code has been published for CVE-2026-35149. Refer to the HCL Software Knowledge Base Article for vendor-supplied technical details.

Detection Methods for CVE-2026-35149

Indicators of Compromise

Authentication success events for DFXServer accounts without corresponding credential validation log entries.
Sessions originating from client IP addresses that were not observed submitting a preceding authentication request.
Unexpected proxy hops or TLS termination points inserted between clients and the DFXServer host.
Access to sensitive DFXServer resources from accounts that did not complete a full authentication handshake.

Detection Strategies

Correlate authentication response events with credential verification events to identify sessions granted access without a matching credential check.
Inspect network telemetry for machine-in-the-middle indicators such as unexpected certificates, downgraded TLS versions, or unusual proxy insertion on paths to the DFXServer host.
Alert on repeated authentication response anomalies from the same client source, which can indicate active response tampering.

Monitoring Recommendations

Forward DFXServer authentication logs and network flow data to a centralized analytics platform for correlation with endpoint and identity telemetry.
Baseline normal authentication flows and alert on deviations in request-response pairing or timing.
Monitor administrative and high-value account activity for access patterns that follow unusual authentication sequences.

How to Mitigate CVE-2026-35149

Immediate Actions Required

Apply the fixed version referenced in the HCL Software Knowledge Base Article as soon as it is available for your deployment.
Restrict network access to DFXServer to trusted management networks and known client subnets until patches are applied.
Enforce TLS with strong cipher suites and validated certificates on all DFXServer client-server communication to raise the bar for response tampering.
Review authentication logs for the past 90 days for anomalous successful logins that lack a corresponding credential validation event.

Patch Information

HCL Software has published remediation guidance in KB0131782. Administrators should consult the article for the specific fixed builds and upgrade steps applicable to their DFXServer deployment.

Workarounds

Terminate DFXServer client connections only at trusted TLS endpoints and disable interception by intermediate proxies.
Segment DFXServer behind a VPN or zero-trust network access gateway to limit exposure to network-positioned attackers.
Enable certificate pinning on clients where supported to prevent silent machine-in-the-middle interception.

bash

# Restrict DFXServer inbound access to a trusted management subnet (example)
iptables -A INPUT -p tcp --dport <dfxserver-port> -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport <dfxserver-port> -j DROP