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Jun 24, 2025
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Update error-526.mdx #23024

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Update error-526.mdx
Kiki-Y123 Jun 13, 2025
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8 changes: 7 additions & 1 deletion ...s/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-526.mdx
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Expand Up @@ -39,6 +39,12 @@ Workers subrequests to any hostname outside your Cloudflare zone that is not pro

As a result, a valid SSL certificate is required at the origin server.

If you are using self-signed SSL certificate at the origin server, use the following workaround to avoid an HTTP Error `526`.

1. Add your self-signed SSL certificate to the **[`Custom Origin Trust Store`](/ssl/origin-configuration/custom-origin-trust-store/)**. This allows the Cloudflare edge to recognize your self-signed SSL certificate as valid.
2. In your Worker's configuration, enable the **[`cots_on_external_fetch` compatibility flag](/workers/configuration/compatibility-flags/#do-not-use-the-custom-origin-trust-store-for-external-subrequests)**. This flag enables the use of the **[`Custom Origin Trust Store`](/ssl/origin-configuration/custom-origin-trust-store/)** when making external (grey-clouded) subrequests from a Cloudflare Worker.


### Resolution

:::note
Expand All @@ -56,4 +62,4 @@ Request your server administrator or hosting provider to review the origin web s

![Screen showing an SSL certificate with no errors.](~/assets/images/support/hc-import-troubleshooting_5xx_errors_sslshopper_output.png)

If the origin server uses a self-signed certificate, configure the domain to use _Full_ _SSL_ instead of _Full SSL (Strict)_. Refer to [recommended SSL settings for your origin](/ssl/origin-configuration/ssl-modes).
If the origin server uses a self-signed certificate, configure the domain to use _Full_ _SSL_ instead of _Full SSL (Strict)_. Refer to [recommended SSL settings for your origin](/ssl/origin-configuration/ssl-modes).