If an X.509 certificate contains a malformed policy constraint and policy processing is enabled, then a write lock will be taken twice recursively. On some operating systems (most widely: Windows) this results in a denial of service when the affected process hangs. Policy processing being enabled on a publicly facing server is not considered to be a common setup. Policy processing is enabled by passing the `-policy' argument to the command line utilities or by calling the `X509_VERIFY_PARAM_set1_policies()' function. Update (31 March 2023): The description of the policy processing enablement was corrected based on CVE-2023-0466.

If an X.509 certificate contains a malformed policy constraint and
policy processing is enabled, then a write lock will be taken twice
recursively.  On some operating systems (most widely: Windows) this
results in a denial of service when the affected process hangs.  Policy
processing being enabled on a publicly facing server is not considered
to be a common setup.

Policy processing is enabled by passing the `-policy'
argument to the command line utilities or by calling the
`X509_VERIFY_PARAM_set1_policies()' function.

Update (31 March 2023): The description of the policy processing enablement
was corrected based on CVE-2023-0466.