Resolving TIA Administrator ERR_SSL_SERVER_CERT_BAD_FORMAT

Resolving TIA Administrator ERR_SSL_SERVER_CERT_BAD_FORMAT on VMware

This technical reference covers the systematic resolution of the ERR_SSL_SERVER_CERT_BAD_FORMAT fault raised by Chromium-based browsers when an engineer attempts to launch the TIA Administrator V3 configuration console hosted inside a VMware virtual machine. The fault blocks the https://localhost:8900/ management URL that the TIA Administrator Windows service binds to by default. The same procedure applies to TIA Administrator running on bare-metal Windows hosts; the VMware layer only adds the network adapter topology that must be validated before certificate trust can be re-established.

Problem Description

After installing TIA Portal V21 (or earlier releases that include the TIA Administrator V3 component) inside a Windows 10/11 guest running on VMware Workstation 17 or VMware vSphere ESXi 8.0, opening https://localhost:8900/ in Microsoft Edge, Google Chrome, or Mozilla Firefox fails immediately with the message:

The connection is not secure
SSL Server certificate format error
ERR_SSL_SERVER_CERT_BAD_FORMAT

The browser never displays the TIA Administrator login page. The same workstation often reports ping localhost as Reply from 127.0.0.1: bytes=32 time<1ms TTL=128, confirming that the IPv4 loopback stack is healthy and that the fault is isolated to the TLS layer.

Root Cause Analysis

The ERR_SSL_SERVER_CERT_BAD_FORMAT error is generated by Chromium's net/socket/ssl_client_socket.cc stack when the X.509 certificate presented by the server violates RFC 5280 structural rules. For TIA Administrator, the root causes observed in field escalations are:

1. Malformed self-signed certificate: The TIA Administrator installer generates a 2048-bit RSA self-signed certificate with CN=localhost, O=Siemens AG, and OU=TIA Portal. If the installation is interrupted, performed under a non-administrator context, or run on a guest whose system clock is offset by more than five minutes, the certificate can be issued with an empty Subject Key Identifier, an empty Authority Key Identifier, or an invalid Not Before timestamp that precedes the UNIX epoch.
2. Trusted root store mismatch: The certificate is not in the Trusted Root Certification Authorities or Trusted People store of the Windows user account that hosts the browser session. Even when the certificate is structurally valid, an untrusted issuer triggers the same Chromium error path before any cipher negotiation occurs.
3. TLS protocol downgrade: Older TIA Portal V13-V15 distributions shipped with TLS 1.0/1.1 servers. Modern browsers (Chrome 110+, Edge 110+, Firefox 115+) have removed support for these protocols, and the resulting handshake failure can surface as ERR_SSL_SERVER_CERT_BAD_FORMAT rather than ERR_SSL_VERSION_OR_CIPHER_MISMATCH.
4. Stale cached certificate: A previously trusted certificate is cached in the browser's cert_db SQLite store, and the new certificate's serial number or public key collides with the cached record.
5. VMware loopback misconfiguration: When the VMware network adapter is configured as Host-Only instead of NAT or Bridged, the localhost binding may resolve to an IPv6 ::1 address that the TIA Administrator service does not bind to. This produces a different certificate chain (or no chain) than the one expected by the browser.

Affected Versions and Platforms

The VMware platform requirements above are taken directly from the official Siemens TIA Portal V21 system requirements documentation. Any virtualization platform that is below VMware Workstation V17, below VMware Player V17, below VMware vSphere Hypervisor (ESXi) 8.0, or below Microsoft Hyper-V Server 2019 is not officially supported and should be upgraded before proceeding.

Diagnostic Procedure

Follow the diagnostic sequence below in the exact order shown. Each step validates one layer of the failure before moving to the next.

Step 1: Validate Loopback Resolution

Open an elevated cmd.exe on the VMware guest and execute:

ping localhost
nslookup localhost
netstat -ano | findstr :8900

Expected output:

• ping localhost resolves to 127.0.0.1 with sub-millisecond RTT.
• nslookup localhost returns Address: 127.0.0.1.
• netstat shows TCP 0.0.0.0:8900 0.0.0.0:0 LISTENING <PID> where PID corresponds to TiaAdministratorV3.exe or sia.exe.

If port 8900 is not in LISTENING state, the TIA Administrator Windows service has not started. Restart the service using services.msc > Siemens TIA Administrator V3 > Restart.

Step 2: Retrieve the Certificate Chain

Export the certificate presented by the TIA Administrator service so its structure can be inspected with OpenSSL. From the VMware guest, run:

openssl s_client -connect localhost:8900 -showcerts > tia_admin_chain.pem 2> tia_admin_handshake.log

Open tia_admin_chain.pem in a text editor. A valid certificate must include the following structural elements in the exact order required by RFC 5280:

0:d=0  hl=4 l= 521 cons: SEQUENCE
4:d=1  hl=4 l= 487 cons: SEQUENCE
  8:d=2  hl=2 l=   3 cons: cont [ 0 ]           <-- Version (MUST be 2 = v3)
 13:d=2  hl=2 l=  20 prim: INTEGER           <-- Serial Number
 35:d=2  hl=2 l=  13 cons: SEQUENCE
 37:d=3  hl=2 l=   9 prim: OBJECT            <-- Signature Algorithm sha256WithRSAEncryption
 48:d=3  hl=2 l=   0 prim: NULL
 50:d=2  hl=2 l=  91 cons: SEQUENCE
 52:d=3  hl=2 l=  11 cons: SET
 54:d=4  hl=2 l=   9 cons: SEQUENCE
 56:d=5  hl=2 l=   3 prim: OBJECT            <-- id-at-commonName
 61:d=5  hl=2 l=   2 prim: UTF8STRING        <-- CN must equal "localhost"

If the dump shows Version: 1 (0x0) or an absent Subject Alternative Name extension, the certificate is malformed and must be regenerated.

Step 3: Validate System Clock and Trust Store

Confirm that the VMware guest clock is synchronized:

w32tm /query /status
w32tm /resync /force

Inspect the trust store for the TIA Administrator certificate:

certlm.msc
Trusted Root Certification Authorities > Certificates
Trusted People > Certificates

Search for entries with Siemens AG as the issuer or localhost as the subject. Note the serial number and expiration date.

Resolution Procedures

Resolution A: Regenerate the TIA Administrator Certificate

The Siemens installation routine regenerates the self-signed certificate when TiaAdministratorV3.exe is reinstalled in repair mode. Execute the following sequence:

1. Close all TIA Portal instances and stop the Windows service Siemens TIA Administrator V3 from services.msc.
2. Open Control Panel > Programs and Features, locate Siemens TIA Administrator V3, and select Repair.
3. When prompted, choose Generate new certificate. The installer writes a fresh 2048-bit RSA certificate with a new serial number and a new Not After timestamp of Current Date + 3650 Days.
4. Restart the service and confirm netstat -ano | findstr :8900 shows the listener re-bound.
5. Open https://localhost:8900/ in a fresh browser session.

Resolution B: Manually Trust the Self-Signed Certificate

If the certificate is structurally valid but untrusted, import it into the appropriate Windows store:

1. From the address bar of Edge or Chrome, click Not secure > Certificate is not valid > Export. Save the file as tia_admin.cer in DER encoded binary X.509 format.
2. Open certlm.msc (Local Machine) and navigate to Trusted Root Certification Authorities > Certificates.
3. Right-click Certificates > All Tasks > Import, select tia_admin.cer, and place it in Trusted Root Certification Authorities.
4. Repeat the import in Trusted People > Certificates to satisfy Firefox, which uses its own trust store.
5. Restart the browser and reload https://localhost:8900/.

Resolution C: Enforce TLS 1.2 or Higher

Older TIA Portal releases default to TLS 1.0. Force the service and the Windows host to negotiate TLS 1.2 by creating the following registry entries on the VMware guest:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server]
"Enabled"=dword:00000000
"DisabledByDefault"=dword:00000001

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server]
"Enabled"=dword:00000000
"DisabledByDefault"=dword:00000001

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]
"Enabled"=dword:00000001
"DisabledByDefault"=dword:00000000

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

Reboot the guest after applying the registry merge. This change is required for any TIA Portal release below V17 when accessed from Chrome 110+, Edge 110+, or Firefox 115+.

Resolution D: Configure the VMware Network Adapter

Confirm that the VMware network adapter mode allows the loopback stack to behave like a standard Windows host:

1. Power off the guest and open VM > Settings > Network Adapter.
2. Select NAT for Workstation/Player or VMXNET3 adapter type for ESXi deployments.
3. Disable IPv6 on the adapter if the certificate was generated for an IPv4-only listener.
4. Re-enable the adapter and restart the guest.

From the host machine, the URL https://<guest-ip>:8900/ should now load. Replace <guest-ip> with the IP shown by ipconfig inside the guest.

Verification Procedure

After applying any of the resolutions above, perform the following verification sequence to confirm that the TIA Administrator console is reachable:

1. Open an elevated PowerShell on the VMware guest and execute Test-NetConnection -ComputerName localhost -Port 8900. The result must show TcpTestSucceeded: True.
2. Run curl -k -v https://localhost:8900/. The verbose log must show SSL connection using TLS_AES_256_GCM_SHA384 or a comparable TLS 1.2/1.3 cipher suite.
3. Open https://localhost:8900/ in a fresh browser profile. The address bar must show the lock icon, and the certificate viewer must display CN=localhost, O=Siemens AG, and a future expiration date.
4. Authenticate with the configured TIA Portal user management credentials and confirm that the User Management, License Management, and Collaboration tabs render without server-side errors.

VMware-Specific Edge Cases

Host-Only Loopback Failure

When the VMware guest is configured with Host-Only networking, the Windows loopback adapter on the guest is bound to a non-routable subnet such as 192.168.56.0/24. Some Chromium versions resolve localhost to the ::1 IPv6 address before the IPv4 127.0.0.1 address, and the TIA Administrator V3 service does not bind to ::1. Disable IPv6 on the VMware network adapter via ncpa.cpl > Properties > Internet Protocol Version 6 (TCP/IPv6) > Uncheck to force IPv4 resolution.

VMXNET3 vs E1000 Adapter

The legacy E1000 emulated adapter introduces a 200-500 ms delay in TLS handshake on the first connection attempt. Switch to VMXNET3 for ESXi guests or vmxnet3 for Workstation guests to remove this delay. The change takes effect after a clean power cycle.

ESXi 8.0 Certificate Pinning

VMware vSphere 8.0 introduces certificate pinning for the management agents. This does not affect guest operating system certificates but may block the host-side browser if the engineer tries to reach the TIA Administrator console through a vSphere Web Client redirection. Always open the guest console directly via VMRC or Workstation Remote Console rather than through the hypervisor UI.

Troubleshooting Matrix

Preventive Maintenance Checklist

• Apply the latest Windows cumulative update (KB5066835 or later) to the VMware guest before any TIA Portal update.
• Synchronize the VMware guest clock to the host using VMware Tools Time Synchronization enabled.
• Document the certificate thumbprint after every TIA Administrator repair-mode reinstall and store it in the engineering change log.
• Use a separate browser profile dedicated to TIA Portal access to prevent cache contamination.
• Maintain VMware Workstation at V17 or higher, VMware Player at V17 or higher, VMware vSphere ESXi at 8.0 U1 or higher, and Microsoft Hyper-V Server at 2019 or higher per the official Siemens system requirements.
• Schedule annual certificate regeneration to prevent expiration-related outages.

When to Escalate to Siemens Support

Escalate to Siemens Industrial Technical Support through the official Siemens Industry Online Support portal when:

• The Repair-mode reinstall fails to regenerate a structurally valid certificate.
• The TIA Administrator service fails to bind to TCP/8900 after multiple restart attempts.
• The certificate chain includes an unexpected intermediate CA that was not generated by Siemens.
• The error persists on bare-metal Windows hardware identical in configuration to the VMware guest, indicating an installation-image-level defect.

Provide the support engineer with the openssl s_client output, the certlm.msc export, the TiaAdministratorV3.log file from %ProgramData%\Siemens\Automation\Logs\, and the exact VMware build string from vmware -v.