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Date: Wed, 22 Apr 2020 08:12:59 +0100
From: Mark J Cox <mark@...nssl.org>
To: oss-security@...ts.openwall.com
Subject: [CVE-2020-1967] OpenSSL 1.1.1d+ Segmentation fault in SSL_check_chain

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OpenSSL Security Advisory [21 April 2020]
=========================================

Segmentation fault in SSL_check_chain (CVE-2020-1967)
=====================================================

Severity: High

Server or client applications that call the SSL_check_chain() function during or
after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a
result of incorrect handling of the "signature_algorithms_cert" TLS extension.
The crash occurs if an invalid or unrecognised signature algorithm is received
from the peer. This could be exploited by a malicious peer in a Denial of
Service attack.

OpenSSL version 1.1.1d, 1.1.1e, and 1.1.1f are affected by this issue.  This
issue did not affect OpenSSL versions prior to 1.1.1d.

Affected OpenSSL 1.1.1 users should upgrade to 1.1.1g

This issue was found by Bernd Edlinger and reported to OpenSSL on 7th April
2020. It was found using the new static analysis pass being implemented in GCC,
- -fanalyzer. Additional analysis was performed by Matt Caswell and Benjamin
Kaduk.

Note
=====

This issue did not affect OpenSSL 1.0.2 however these versions are out of
support and no longer receiving public updates. Extended support is available
for premium support customers: https://www.openssl.org/support/contracts.html

This issue did not affect OpenSSL 1.1.0 however these versions are out of
support and no longer receiving updates.

Users of these versions should upgrade to OpenSSL 1.1.1.

References
==========

URL for this Security Advisory:
https://www.openssl.org/news/secadv/20200421.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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