OpenSSL Security Advisory

[Tomas Mraz]

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Excessive Resource Usage Verifying X.509 Policy Constraints (CVE-2023-0464)
===========================================================================

Severity: Low

A security vulnerability has been identified in all supported versions
of OpenSSL related to the verification of X.509 certificate chains
that include policy constraints.  Attackers may be able to exploit this
vulnerability by creating a malicious certificate chain that triggers
exponential use of computational resources, leading to a denial-of-service
(DoS) attack on affected systems.

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

OpenSSL 3.1, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.

Due to the low severity of this issue we are not issuing new releases of
OpenSSL at this time. The fix will be included in the next releases when they
become available. The fix is also available in commit 2017771e (for 3.1),
commit 959c59c7 (for 3.0), commit 879f7080 (for 1.1.1) in the OpenSSL
git repository, and commit 2dcd4f1e (for 1.0.2) in the OpenSSL git
repository for premium customers.

Once they are released:

OpenSSL 3.1 users should upgrade to 3.1.1.
OpenSSL 3.0 users should upgrade to 3.0.9.
OpenSSL 1.1.1 users should upgrade to 1.1.1u.
OpenSSL 1.0.2 users should upgrade to 1.0.2zh (premium support customers only).

This issue was reported on 12th January 2023 by David Benjamin (Google).
The fix was developed by Dr Paul Dale.

OpenSSL 1.1.1 will reach end-of-life on 2023-09-11. After that date security
fixes for 1.1.1 will only be available to premium support customers.

References
==========

URL for this Security Advisory:
https://www.openssl.org/news/secadv/20230322.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
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