437
SIP
437 Unsupported Certificate
The server was unable to validate the certificate referenced by the Identity-Info header. The certificate may be self-signed or from an untrusted CA.
On this page
When You See This Code
When the signing certificate for SIP Identity validation is not trusted by the verifying server.
How to Fix
Use a certificate from a trusted Certificate Authority. Ensure the certificate chain is complete and not expired.
Specification
Compare With
Guides
401 Unauthorized vs 403 Forbidden: When to Use Each
Security & Authentication
SIP Response Codes: Understanding VoIP Call Flow
Real-Time Protocols
SIP Call Flow: Understanding Session Setup
Real-Time Protocols
WebRTC Signaling with SIP and WebSocket
Real-Time Protocols
RFC 3261: SIP Protocol Deep Dive
Protocol Deep Dives
TLS 1.3: Faster, Simpler, More Secure
Protocol Deep Dives
Glossary
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Request Method (HTTP Verb)
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Port Number
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Socket
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RFC (Request for Comments)
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Codec Negotiation
SIP Response Classes
VoIP (Voice over IP)
Presence (SIP)
PBX (Private Branch Exchange)
MFA (Multi-Factor Authentication)
TLS Versions
Frequently Asked Questions
What is SIP 437 Unsupported Certificate?
The server was unable to validate the certificate referenced by the Identity-Info header. The certificate may be self-signed or from an untrusted CA.
When do you see SIP 437 Unsupported Certificate?
When the signing certificate for SIP Identity validation is not trusted by the verifying server.
How to fix SIP 437 Unsupported Certificate?
Use a certificate from a trusted Certificate Authority. Ensure the certificate chain is complete and not expired.