Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Forum Discussion

cf_525_pain_310's avatar
cf_525_pain_310
Icon for Nimbostratus rankNimbostratus
Feb 16, 2017

CloudFlare 525 Errors - f5 fix?

I recently started routing assets called via https through Cloudflare, a proxy service, amongst other things.   I have an interesting issue where, once i did that, i saw that around 1% of browser ...
big-ip
devops
irules
security
Vijay_E's avatar
Vijay_E
Icon for Cirrus rankCirrus
Feb 16, 2017

Basic questions:

 

  1. Have you verified that the SSL cipher suite between cloudflare and F5 are compatible ?
  2. SNI enabled/disabled ?
  3. Have you tested with SSL terminating directly on the server(s) or a test server ?
  4. Any weird logs on the F5 ?
  5. Did this error exist since the initial set up or was noticed recently after a change like code upgrade/downgrade ?