ERR_SSL_RENEGOTIATION_NOT_SUPPORTED

Enterno.io Editorial Team

By Anatoly Oshmanovsky · Updated Apr 17, 2026

Key idea:

ERR_SSL_RENEGOTIATION_NOT_SUPPORTED — server requested renegotiation (rekey), but the client (or protocol) does not support it. TLS 1.3 removed renegotiation entirely (security issue). If the server still initiates, downgrade to TLS 1.2 or (better) remove the renegotiation logic. Typical in mTLS/client-auth workflows.

This error blocks HTTPS access. Below: causes, fixes, working config, FAQ.

Try it now — free →

Common Causes

TLS 1.3 removed renegotiation — server still tries
mTLS (client-auth): server requests cert after handshake via re-neg
Legacy Java applications with renegotiation-based key refresh
Apache + SSLVerifyClient require inside
Old JVM (

Step-by-Step Fix

TLS 1.3: move to post-handshake authentication (RFC 8446)
TLS 1.2 + mTLS: request clientauth at port/host level, not via re-neg
nginx + mTLS: ssl_verify_client optional_no_ca; ssl_client_certificate
Remove renegotiation from client pool/library settings
Update client Java/OpenSSL/curl to TLS 1.3 support

Check SSL Certificate →

Related SSL Errors

CertificateExpiry, issuer, domains (SAN)

ChainIntermediate and root CA validation

TLS ProtocolTLS version and cipher suite

VulnerabilitiesHeartbleed, POODLE, weak ciphers

Why teams trust us

TLS 1.3

supported

Full

CA chain check

<2s

result

30/14/7

days-to-expiry alerts

How it works

Enter domain

TLS chain verified

Expiry date & vulnerabilities

What Does the SSL Check Cover?

SSL/TLS is the encryption protocol that protects data between the browser and server. Our tool analyzes the certificate, chain of trust, TLS version, and knownvulnerabilities.

Certificate Details

Issuer, validity period, signature algorithm, covered domains (SAN), and validation type (DV/OV/EV).

Chain of Trust

Full chain verification: from leaf certificate through intermediates to root CA.

TLS Analysis

Protocol version (TLS 1.2/1.3), cipher suites, Perfect Forward Secrecy (PFS) support.

Expiry Alerts

Set up a monitor — get Telegram and email alerts 30/14/7 days before expiration.

DV vs OV vs EV Certificates

DV (Domain Validation)

Confirms domain ownership only
Issued in minutes automatically
Free via Let's Encrypt
Suitable for most websites
Most common certificate type

OV / EV

Organization (OV) or Extended Validation (EV)
Issued in 1-5 business days
Costs $50 to $500/year
For finance, e-commerce, government sites
Increases user trust

Who uses this

DevOps

SSL certificate monitoring

Security

TLS config audit

SEO

HTTPS as ranking factor

E-commerce

customer trust

Common Mistakes

❌

Expired certificateBrowsers block sites with expired SSL. Set up auto-renewal or monitoring.

❌

Incomplete certificate chainWithout intermediate CA, some browsers and bots cannot verify the certificate.

❌

Mixed content on HTTPS siteHTTP resources on an HTTPS page — the browser lock icon disappears, reducing trust.

❌

Using TLS 1.0/1.1Legacy TLS versions have known vulnerabilities. Use TLS 1.2+ or 1.3.

❌

Domain mismatch in certificateThe certificate must cover all site domains, including www and subdomains.

Best Practices

✓

Set up auto-renewalLet's Encrypt + certbot with cron — certificate renews automatically every 60-90 days.

✓

Enable HSTSStrict-Transport-Security header forces browsers to always use HTTPS.

✓

Use TLS 1.3TLS 1.3 is faster (1-RTT handshake) and safer — legacy ciphers removed.

✓

Monitor expiration datesCreate a monitor on Enterno.io — get notified well before expiration.

✓

Verify chain after renewalAfter certificate renewal, confirm that intermediate certificates are installed.

Get more with a free account

SSL certificate monitoring, check history and alerts 30 days before expiry.

Learn more

How-to

Glossary

Research

TLS Cipher Suites 2026: Distribution Report

Errors

Alternatives

Frequently Asked Questions

What is TLS renegotiation?

A process during an active TLS session where parties renegotiate keys/cipher/auth without tearing down the connection. TLS 1.3 replaced it with post-handshake auth.

Why was renegotiation removed?

Vulnerable to attack (CVE-2009-3555 renegotiation MITM). TLS 1.3 uses KeyUpdate and post-handshake auth — safer replacement.

How to set up mTLS in 2026?

For TLS 1.3: server sends CertificateRequest in handshake, client answers. No renegotiation. Nginx supports.

Legacy Java client — what to do?

Upgrade to Java 17+ (TLS 1.3 support). Or keep TLS 1.2 for this endpoint + set up mTLS correctly.