Firefox 36 (released 2015-02-24) drops support for many / most 1024 certs.
It is "early 2015" - https://blog.mozilla.org/security/2015/01/28/phase-2-phasing-out-certificates-with-1024-bit-rsa-keys/
You might want to check your intermediate cert signatures for weak certs in the chain.
The chart here looks like a bit of springtime fun:
As the article above says, it might be good to check for other services (imaps, pop3s, STARTTLS, or random SSL services) as client libraries or applications drop support for weaker certs.
For a quick test (using curl's built in certs) - curl -Iv https://site.to.test
Here is an example with a failed check:
$ curl -Iv https://www.supersecuresite.local * About to connect() to www.supersecuresite.local port 443 (#0) * Trying 192.168.42.42... connected * Connected to www.supersecuresite.local (192.168.42.42) port 443 (#0) * successfully set certificate verify locations: * CAfile: /usr/share/curl/ca-bundle.crt CApath: none * SSLv3, TLS handshake, Client hello (1): * SSLv3, TLS handshake, Server hello (2): * SSLv3, TLS handshake, CERT (11): * SSLv3, TLS alert, Server hello (2): * SSL certificate problem, verify that the CA cert is OK. Details: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed * Closing connection #0 curl: (60) SSL certificate problem, verify that the CA cert is OK. Details: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed More details here: http://curl.haxx.se/docs/sslcerts.html curl performs SSL certificate verification by default, using a "bundle" of Certificate Authority (CA) public keys (CA certs). If the default bundle file isn't adequate, you can specify an alternate file using the --cacert option. If this HTTPS server uses a certificate signed by a CA represented in the bundle, the certificate verification probably failed due to a problem with the certificate (it might be expired, or the name might not match the domain name in the URL). If you'd like to turn off curl's verification of the certificate, use the -k (or --insecure) option.