OpenSSL Overflow in rsaz_1024_mul_avx2() Lets Remote Users Obtain Potentially Sensitive Information in Certain Cases and SSL_read()/SSL_write() Error State Bug May Bypass Decryption/Encryption in Certain Application Dependent Cases
SecurityTracker Alert ID: 1039978|
SecurityTracker URL: http://securitytracker.com/id/1039978
(Links to External Site)
Updated: Mar 27 2018|
Original Entry Date: Dec 7 2017
Disclosure of authentication information, Disclosure of user information|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): prior to 1.0.2n|
Two vulnerabilities were reported in OpenSSL. A remote user can obtain potentially sensitive information on the target system in certain cases. A remote user may be able to cause an application to bypass decryption/encryption in certain limited cases.|
A remote user can exploit an overflow bug in the AVX2 Montgomery multiplication procedure used in exponentiation with 1024-bit moduli to potentially determine information about the private key in certain situations [CVE-2017-3738].
Processors that support the AVX2 but not ADX extensions (e.g., Intel Haswell (4th generation)) are affected.
Attacks against DH1024 may be feasible.
EC algorithms are not affected.
A remote user can invoke a handshake failure to trigger a bug in OpenSSL error handling code for applications that directly make an SSL_read() or SSL_write() call for an SSL object after receiving a fatal error, causing data to bypass the decryption or encryption process [CVE-2017-3737]. Versions 1.0.2b and after are affected.
David Benjamin (Google) reported these vulnerabilities.
A remote user can potentially determine information about the private key in certain situations.|
A remote user may be able to cause an application to bypass decryption/encryption in certain limited cases.
The vendor has issued a fix (1.0.2n).|
[Editor's note: The fix for CVE-2017-3738 for version 1.1.0 is available in version 1.1.0h.]
The vendor advisories are available at:
Vendor URL: www.openssl.org/news/secadv/20171207.txt (Links to External Site)
Boundary error, State error|
|Underlying OS: Linux (Any), UNIX (Any), Windows (Any)|
This archive entry has one or more follow-up message(s) listed below.|
Source Message Contents
Subject: [openssl-announce] OpenSSL Security Advisory|
-----BEGIN PGP SIGNED MESSAGE-----
OpenSSL Security Advisory [07 Dec 2017]
Read/write after SSL object in error state (CVE-2017-3737)
OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state"
mechanism. The intent was that if a fatal error occurred during a handshake then
OpenSSL would move into the error state and would immediately fail if you
attempted to continue the handshake. This works as designed for the explicit
handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()),
however due to a bug it does not work correctly if SSL_read() or SSL_write() is
called directly. In that scenario, if the handshake fails then a fatal error
will be returned in the initial function call. If SSL_read()/SSL_write() is
subsequently called by the application for the same SSL object then it will
succeed and the data is passed without being decrypted/encrypted directly from
the SSL/TLS record layer.
In order to exploit this issue an application bug would have to be present that
resulted in a call to SSL_read()/SSL_write() being issued after having already
received a fatal error.
This issue does not affect OpenSSL 1.1.0.
OpenSSL 1.0.2 users should upgrade to 1.0.2n
This issue was reported to OpenSSL on 10th November 2017 by David Benjamin
(Google). The fix was proposed by David Benjamin and implemented by Matt Caswell
of the OpenSSL development team.
rsaz_1024_mul_avx2 overflow bug on x86_64 (CVE-2017-3738)
There is an overflow bug in the AVX2 Montgomery multiplication procedure
used in exponentiation with 1024-bit moduli. No EC algorithms are affected.
Analysis suggests that attacks against RSA and DSA as a result of this defect
would be very difficult to perform and are not believed likely. Attacks
against DH1024 are considered just feasible, because most of the work
necessary to deduce information about a private key may be performed offline.
The amount of resources required for such an attack would be significant.
However, for an attack on TLS to be meaningful, the server would have to share
the DH1024 private key among multiple clients, which is no longer an option
This only affects processors that support the AVX2 but not ADX extensions
like Intel Haswell (4th generation).
Note: The impact from this issue is similar to CVE-2017-3736, CVE-2017-3732
Due to the low severity of this issue we are not issuing a new release of
OpenSSL 1.1.0 at this time. The fix will be included in OpenSSL 1.1.0h when it
becomes available. The fix is also available in commit e502cc86d in the OpenSSL
OpenSSL 1.0.2 users should upgrade to 1.0.2n
This issue was reported to OpenSSL on 22nd November 2017 by David Benjamin
(Google). The issue was originally found via the OSS-Fuzz project. The fix was
developed by Andy Polyakov of the OpenSSL development team.
Support for version 1.0.1 ended on 31st December 2016. Support for versions
0.9.8 and 1.0.0 ended on 31st December 2015. Those versions are no longer
receiving security updates.
URL for this Security Advisory:
Note: the online version of the advisory may be updated with additional details
For details of OpenSSL severity classifications please see:
-----BEGIN PGP SIGNATURE-----
-----END PGP SIGNATURE-----
openssl-announce mailing list
To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-announce