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Date: Sat, 27 Mar 2021 19:02:56 +0100
From: Solar Designer <>
Subject: OpenSSL 1.1.1 CVE-2021-3450 CA certificate check bypass with X509_V_FLAG_X509_STRICT, CVE-2021-3449 NULL pointer deref in signature_algorithms processing


As many of you are aware, the OpenSSL project provides pre-notification
of vulnerability disclosures.  The way they do it is by posting to the
public OpenSSL mailing lists (see "Forthcoming OpenSSL release" below)
and by contacting specific other projects/channels with an offer to
provide the actual detail more privately only to those interested in
such detail.  This time, not unlike other times, there was a message to
the distros list with content similar to the public "Forthcoming OpenSSL
release" below plus the offer I mentioned.  Since the message itself did
not contain any vulnerability detail, it might not strictly fall under
the distros list policy of requiring a subsequent oss-security posting,
but I think it's preferable to proceed with such postings in such cases.
So I am doing that now (the "OpenSSL Security Advisory" below), and I'd
like the OpenSSL project itself to be doing it going forward.

One other detail I feel I have to bring up in here, and expect a
response to, is Wind River's apparent leak of the vulnerability detail
two days prior to scheduled public disclosure.  This was brought up on
the distros list back then, and I was also asked about it on Twitter
when the vulnerabilities were finally made public appropriately on the
scheduled date.

Since the vulnerability detail wasn't on the distros list, it's not
exactly a case of a list member leaking from there, but it's closely
related.  And regardless of where this happened, it's a concern, which
we probably should discuss on oss-security.

So I'd appreciate an explanation/statement from Wind River on what
happened and what measures, if any, are being taken to prevent this from
happening again.  I'd also appreciate a comment from OpenSSL.

The leak was on a web page archived here:

As I recall, the private GitHub links in there gave me "404 Not Found"
soon after the link (which was live at the time, not
needing was sent to the distros list by a concerned fellow
distro.  This means that either OpenSSL promptly brought them down or
they were only ever accessible under appropriately privileged GitHub
accounts.  In the latter case, the existence of that web page with its
content might not have been that much of a leak, as in addition to the
public pre-notification the web page only contained CVE IDs and one-line
vulnerability titles and commit hashes and those GitHub links.  If the
actual commits and the links were never publicly accessible, then it
wasn't that much of an issue and reasonably didn't require considering
the embargo broken.

Another concern I have is that I have to write this to ever hear from
Wind River.  I'd have expected them to comment on the distros list the
moment this was brought up in there - but they kept silent.  Did they
even see the message?  (Of course, I could ask privately, but the
concerns are already public and we need to discuss this in public.)

To summarize, this is probably not a big deal, but let's figure out what
happened and what can be done better next time.



----- Forwarded message from Matt Caswell <> -----

To: "" <>,,
 "" <>
From: Matt Caswell <>
Subject: Forthcoming OpenSSL release
Date: Mon, 22 Mar 2021 09:18:12 +0000

The OpenSSL project team would like to announce the forthcoming
release of OpenSSL version 1.1.1k.

This release will be made available on Thursday 25th March 2021
between 1300-1700 UTC.

OpenSSL 1.1.1k is a security-fix release. The highest severity issue
fixed in this release is HIGH:


The OpenSSL Project Team

----- End forwarded message -----

----- Forwarded message from OpenSSL <> -----

Date: Thu, 25 Mar 2021 14:03:24 +0000
From: OpenSSL <>
 OpenSSL User Support ML <>,
 OpenSSL Announce ML <>
Subject: OpenSSL Security Advisory

Hash: SHA256

OpenSSL Security Advisory [25 March 2021]

CA certificate check bypass with X509_V_FLAG_X509_STRICT (CVE-2021-3450)

Severity: High

The X509_V_FLAG_X509_STRICT flag enables additional security checks of the
certificates present in a certificate chain. It is not set by default.

Starting from OpenSSL version 1.1.1h a check to disallow certificates in
the chain that have explicitly encoded elliptic curve parameters was added
as an additional strict check.

An error in the implementation of this check meant that the result of a
previous check to confirm that certificates in the chain are valid CA
certificates was overwritten. This effectively bypasses the check
that non-CA certificates must not be able to issue other certificates.

If a "purpose" has been configured then there is a subsequent opportunity
for checks that the certificate is a valid CA.  All of the named "purpose"
values implemented in libcrypto perform this check.  Therefore, where
a purpose is set the certificate chain will still be rejected even when the
strict flag has been used. A purpose is set by default in libssl client and
server certificate verification routines, but it can be overridden or
removed by an application.

In order to be affected, an application must explicitly set the
X509_V_FLAG_X509_STRICT verification flag and either not set a purpose
for the certificate verification or, in the case of TLS client or server
applications, override the default purpose.

OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these
versions should upgrade to OpenSSL 1.1.1k.

OpenSSL 1.0.2 is not impacted by this issue.

This issue was reported to OpenSSL on 18th March 2021 by Benjamin Kaduk
from Akamai and was discovered by Xiang Ding and others at Akamai. The fix was
developed by Tom???? Mr??z.

NULL pointer deref in signature_algorithms processing (CVE-2021-3449)

Severity: High

An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation
ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits
the signature_algorithms extension (where it was present in the initial
ClientHello), but includes a signature_algorithms_cert extension then a NULL
pointer dereference will result, leading to a crash and a denial of service

A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which
is the default configuration). OpenSSL TLS clients are not impacted by this

All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions
should upgrade to OpenSSL 1.1.1k.

OpenSSL 1.0.2 is not impacted by this issue.

This issue was reported to OpenSSL on 17th March 2021 by Nokia. The fix was
developed by Peter K??stle and Samuel Sapalski from Nokia.


OpenSSL 1.0.2 is out of support and no longer receiving public updates. Extended
support is available for premium support customers:

OpenSSL 1.1.0 is out of support and no longer receiving updates of any kind.
The impact of these issues on OpenSSL 1.1.0 has not been analysed.

Users of these versions should upgrade to OpenSSL 1.1.1.


URL for this Security Advisory:

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

For details of OpenSSL severity classifications please see:


----- End forwarded message -----

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