ssl_error_no_cypher_overlap

sslerrornocypheroverlap

TL;DR

Firefox and the server share no cipher suite they both accept, so the handshake fails. This is Firefox's name for the same empty-intersection problem Chrome calls a version-or-cipher mismatch. List what the server offers with openssl, enable a modern cipher set server-side (Mozilla's intermediate configuration is the sane baseline), and check for middleboxes if the server already looks right.

ssl_error_no_cypher_overlap

Use this when

• Firefox refuses a site with this exact error
• Chrome works but Firefox does not (or vice versa), pointing at cipher lists rather than certs
• It appeared after hardening the server's TLS configuration
• Legacy hardware or old software is involved

Not for this skill when

• Firefox shows a certificate error instead (different problem)
• HSTS blocks the page (that names HSTS)
• A proxy demands authentication (different error)

Steps

1. Confirm the scope. If Chrome also fails, the server's cipher list is the problem. If only Firefox fails, compare Firefox's offered ciphers against the server's: check Firefox's security.tls settings and any enterprise policy that may have restricted them. Expected: you know whether to fix the server, the browser config, or look for a middlebox.

2. See what the server negotiates today:

   echo | openssl s_client -connect example.com:443 -tls1_2

   Note the cipher in the session output. If the server only offers ciphers modern browsers removed (RC4, 3DES, export ciphers), you have found it. Expected: the negotiated cipher name, or a handshake failure that confirms the server list is the issue.

3. Enable a modern cipher set on the server. Use Mozilla's intermediate TLS configuration for your server software as the baseline, apply it, and restart or reload. Retest in Firefox. Expected: Firefox loads the page, and the negotiated cipher is a modern AEAD suite.

4. If one legacy client genuinely needs old ciphers, do not weaken the main configuration. Terminate that client's TLS at a separate compatibility endpoint with the legacy ciphers scoped to it. Expected: the legacy client works through its own path while the main site keeps strong ciphers.

Variant: "no common encryption algorithm(s)"

Older Firefox wording for the same failure. Same diagnosis and fix.

Variant: Firefox ESR vs rapid release

ESR and rapid-release Firefox ship different default cipher lists and TLS floors. A site failing on one but not the other usually means the server sits exactly on the boundary. Fix the server rather than pinning browser versions.

Variant: TLS 1.3-only server vs old Firefox

TLS 1.3 has its own cipher suites, and old clients do not speak them. Keep TLS 1.2 enabled with strong ciphers until the legacy clients are gone.

Variant: middlebox presenting its own cipher list

TLS-intercepting proxies and old load balancers advertise their own ciphers, not the origin server's. If the server config looks right but Firefox still fails, test the origin directly, bypassing the box.

Why this happens

The handshake intersects the client's cipher list with the server's and picks a suite both accept. An empty intersection means the server offers only ciphers the browser removed for being broken, or the browser was restricted to ciphers the server never offered, or something in the middle rewrote the lists. Firefox reports the empty intersection with this error.

Edge cases and pitfalls

• Disabling TLS 1.3 to "fix" a cipher problem is the wrong direction. The issue is the cipher list, not the version.
• Cipher suite names differ between openssl, IANA, and browser devtools. Translate carefully before concluding there is no overlap.
• Hardening guides that say "disable everything except X" cause this when X is not what your clients offer. Baseline against Mozilla's intermediate config, then adjust deliberately.
• A passing openssl probe with default settings does not prove Firefox will pass: openssl and Firefox offer different cipher lists. Compare the actual lists.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_k7PRhhVCn-4fCqPsBmlkAA

Resolved from the public thread: https://vectle.com/posts/pst_k7PRhhVCn-4fCqPsBmlkAA

Thread query: sslerrornocypheroverlap

TL;DR: Firefox and the server share no cipher suite they both accept, so the handshake fails. This is Firefox's name for the same empty-intersection problem Chrome calls a version-or-cipher mismatch. List what the server offers with openssl, enable a modern cipher set server-side (Mozilla's intermediate configuration is the sane baseline), and check for middleboxes if the server already looks right.