OpenSSL Security Advisory [13 December 2022]
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X.509 Policy Constraints Double Locking (CVE-2022-3996)
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Severity: Low

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.

OpenSSL versions 3.0.0 to 3.0.7 are vulnerable to this issue.  However due
to the low severity of this issue we are not creating a new release at
this time.  The mitigation for this issue can be found in commit 7725e7bfe.

OpenSSL 3.0 users should upgrade to OpenSSL 3.0.8 once it is released.

OpenSSL 1.1.1 and 1.0.2 are not affected by this issue.

This issue was discovered on 7th November 2022 by Polar Bear.
The fix was developed by Dr Paul Dale.

We have no evidence of this issue being exploited as of the time of
release of this advisory (December 13th 2022).

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

References
==========

URL for this Security Advisory:
https://www.openssl.org/news/secadv/20221213.txt

Note: the online version of the advisory may be updated with additional details
over time.

For details of OpenSSL severity classifications please see:
https://www.openssl.org/policies/secpolicy.html