CERT Advisory CA-2002-23 Multiple Vulnerabilities In OpenSSL
Original release date: July 30, 2002
Last revised: --
Source: CERT/CC
A complete revision history can be found at the end of this file.
Systems Affected
* OpenSSL prior to 0.9.6e, up to and including pre-release
0.9.7-beta2
* OpenSSL pre-release 0.9.7-beta2 and prior with Kerberos enabled
* SSLeay library
Overview
There are four remotely exploitable buffer overflows in OpenSSL. There
are also encoding problems in the ASN.1 library used by OpenSSL.
Several of these vulnerabilities could be used by a remote attacker to
execute arbitrary code on the target system. All could be used to
create denial of service.
I. Description
OpenSSL is a widely deployed, open source implementation of the Secure
Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1)
protocols as well as a full-strength general purpose cryptography
library. The SSL and TLS protocols are used to provide a secure
connection between a client and a server for higher level protocols
such as HTTP. Four remotely exploitable vulnerabilities exist in many
OpenSSL client and server systems.
VU#102795 - OpenSSL servers contain a buffer overflow during the SSLv2
handshake process
Versions of OpenSSL servers prior to 0.9.6e and pre-release version
0.9.7-beta2 contain a remotely exploitable buffer overflow
vulnerability. This vulnerability can be exploited by a client
using a malformed key during the handshake process with an SSL
server connection. Note that only SSLv2-supported sessions are
affected by this issue.
This issue is also being referenced as CAN-2002-0656.
VU#258555 - OpenSSL clients contain a buffer overflow during the SSLv3
handshake process
OpenSSL clients using SSLv3 prior to version 0.9.6e and pre-release
version 0.9.7-beta2 contain a buffer overflow vulnerability. A
malicious server can exploit this by sending a large session ID to
the client during the handshake process.
This issue is also being referenced as CAN-2002-0656.
VU#561275 - OpenSSL servers with Kerberos enabled contain a remotely
exploitable buffer overflow vulnerability during the SSLv3 handshake
process
Servers running OpenSSL pre-release version 0.9.7 with Kerberos
enabled contain a remotely exploitable buffer overflow
vulnerability. This vulnerability can be exploited by a malicious
client sending a malformed key during the SSLv3 handshake process
with the server.
This issue is also being referenced as CAN-2002-0657.
VU#308891 - OpenSSL contains multiple buffers overflows in buffers
that are used to hold ASCII representations of integers
OpenSSL clients and servers prior to version 0.9.6e and pre-release
version 0.9.7-beta2 contain multiple remotely exploitable buffer
overflow vulnerabilities if running on 64-bit platforms. These
buffers are used to hold ASCII representations of integers.
This issue is also being referenced as CAN-2002-0655.
In addition, a separate issue has been identified in OpenSSL involving
malformed ASN.1 encodings. Affected components include SSL or TLS
applications, as well as S/MIME, PKCS#7, and certificate creation
routines.
VU#748355 - ASN.1 encoding errors exist in implementations of SSL,
TLS, S/MIME, PKCS#7 routines
The ASN.1 library used by OpenSSL has various encoding errors that
allow malformed certificate encodings to be parsed incorrectly.
Exploitation of this vulnerability can lead to remote
denial-of-service issues. Routines affected include those
supporting SSL and TLS applications, as well as those supporting
S/MIME, PKCS#7, and certificate creation.
This issue is also being referenced as CAN-2002-0659.
Although these vulnerabilities affect OpenSSL, other implementations
of the SSL protocol that use or share a common code base may be
affected. This includes implementations that are derived from the
SSLeay library developed by Eric A. Young and Tim J. Hudson.
As noted in the OpenSSL advisory as well, sites running OpenSSL 0.9.6d
servers on 32-bit platforms with SSLv2 handshaking disabled will not
be affected by any of the buffer overflows described above. However,
due to the nature of the ASN.1 encoding errors, such sites may still
be affected by denial-of-service situations.
II. Impact
By exploiting the buffer overflows above, a remote attacker can
execute arbitrary code on a vulnerable server or client system or
cause a denial-of-service situation. Exploitation of the ASN.1
encoding errors can lead to a denial of service.
III. Solution
Apply a patch from your vendor
Appendix A contains information provided by vendors for this advisory.
As vendors report new information to the CERT/CC, we will update this
section and note the changes in our revision history. If a particular
vendor is not listed below or in the individual vulnerability notes,
we have not received their comments. Please contact your vendor
directly.
Upgrade to version 0.9.6e of OpenSSL
Upgrade to version 0.9.6e of OpenSSL to resolve the issues addressed
in this advisory. As noted in the OpenSSL advisory, separate patches
are available:
Combined patches for OpenSSL 0.9.6d:
http://www.openssl.org/news/patch_20020730_0_9_6d.txt
After either applying the patches above or upgrading to 0.9.6e,
recompile all applications using OpenSSL to support SSL or TLS
services, and restart said services or systems. This will eliminate
all known vulnerable code.
Sites running OpenSSL pre-release version 0.9.7-beta2 may wish to
upgrade to 0.9.7-beta3, which corrects these vulnerabilities. Separate
patches are available as well:
Combined patches for OpenSSL 0.9.7 beta 2:
http://www.openssl.org/news/patch_20020730_0_9_7.txt
Disable vulnerable applications or services
Until fixes for these vulnerabilities can be applied, disable all
applications that use vulnerable implementations of OpenSSL. Systems
with OpenSSL 0.9.7 pre-release with Kerberos enabled also need to
disable Kerberos to protect against VU#561275. As a best practice, the
CERT/CC recommends disabling all services that are not explicitly
required. Before deciding to disable SSL or TLS, carefully consider
the impact that this will have on your service requirements.
Disabling SSLv2 handshaking will prevent exploitation of VU#102795.
However, due to the nature of the ASN.1 encoding errors, such sites
would still be vulnerable to denial-of-service attacks.
Appendix A. - Vendor Information
This appendix contains information provided by vendors for this
advisory. As vendors report new information to the CERT/CC, we will
update this section and note the changes in our revision history. If a
particular vendor is not listed below or in the individual
vulnerability notes, we have not received their comments.
OpenLDAP
The OpenLDAP Project uses OpenSSL. Rebuilding OpenLDAP with updated
versions of OpenSSL should adequately address reported issues.
Those using packaged versions of OpenLDAP should contact the
package distributor for update information.
OpenSSL
Please see http://www.openssl.org/news/secadv_20020730.txt.
Red Hat
Red Hat distributes affected versions of OpenSSL in all Red Hat
Linux distributions as well as the Stronghold web server. Red Hat
Linux errata packages that fix the above vulnerabilities
(CAN-2002-0655 and CAN-2002-0656) are available from the URL below.
Users of the Red Hat Network are able to update their systems using
the 'up2date' tool. A future update will fix the potential remote
DOS in the ASN.1 encoding (CAN-2002-0659)
http://rhn.redhat.com/errata/RHSA-2002-155.html
_________________________________________________________________
These vulnerabilities were discovered and reported by the following:
* VU#102795 - discovered by A.L. Digital Ltd and independently
discovered and reported by John McDonald of Neohapsis
* VU#258555, VU#561275, VU#308891 - discovered by A.L. Digital Ltd
* VU#748355 - discovered by Adi Stav and James Yonan independently
The CERT/CC thanks the OpenSSL team for the work they put into their
advisory, on which this document is largely based.
_________________________________________________________________
Feedback can be directed to the authors: Jason A. Rafail, Cory F.
Cohen, Jeffrey S. Havrilla, Shawn V. Hernan.
______________________________________________________________________
This document is available from:
http://www.cert.org/advisories/CA-2002-23.html
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Revision History
July 30, 2002: Initial release