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OpenSSL 0.9.6k does not properly handle ASN.1 sequences

Vulnerability Note VU#412478

Original Release Date: 2003-11-04 | Last Revised: 2003-11-05

Overview

A vulnerability in the way OpenSSL handles ASN.1 elements could allow a remote attacker to cause a denial of service on systems running Microsoft Windows.

Description

OpenSSL implements the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols and includes a general purpose cryptographic library. SSL and TLS are commonly used to provide authentication, encryption, integrity, and non-repudiation services to network applications such as HTTP, IMAP, POP3, LDAP, and others. Clients and servers exchange authentication information in X.509 certificates. While the SSL and TLS protocols are not directly based on ASN.1, they do rely on ASN.1 objects used in X.509 certificates and other cryptographic elements (e.g. PKCS#1 encoded RSA values).

OpenSSL 0.9.6k does not properly handle certain ASN.1 sequences. As a result, OpenSSL performs a recursive function call that could exhaust system resources and crash the process using the OpenSSL library. This denial-of-service condition has only been observed on Microsoft Windows platforms. OpenSSL 0.9.7 is not affected.

From the OpenSSL advisory:

A bug in OpenSSL 0.9.6 would cause certain ASN.1 sequences to triggera large recursion.  On platforms such as Windows this large recursioncannot be handled correctly and so the bug causes OpenSSL to crash.  Aremote attacker could exploit this flaw if they can send arbitraryASN.1 sequences which would cause OpenSSL to crash.  This could beperformed for example by sending a client certificate to a SSL/TLSenabled server which is configured to accept them.

The U.K. National Infrastructure Security Co-ordination Centre (NISCC) is tracking this vulnerability as NISCC/006489/openssl2.

Impact

By providing specially crafted ASN.1 encoded data to a vulnerable system, a remote attacker could cause a denial of service by consuming system resources. This has only been observed on Microsoft Windows systems. One potential attack vector is a client certificate message containing specially crafted X.509 certificates. Note that OpenSSL versions 0.9.7c or 0.9.6k and above do not accept unsolicited client certificates (VU#732952).

Solution

Upgrade or Patch
Upgrade to OpenSSL 0.9.7c or 0.9.6l. Alternatively, upgrade or apply a patch as specified by your vendor. Further information is available in an advisory from OpenSSL. Note that it is necessary to recompile any applications that are statically linked to OpenSSL libraries.

Vendor Information

412478
 
Affected   Unknown   Unaffected

OpenSSL

Notified:  November 04, 2003 Updated:  November 04, 2003

Status

  Vulnerable

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

Please see <http://www.openssl.org/news/secadv_20031104.txt>.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Alcatel

Notified:  November 04, 2003 Updated:  November 04, 2003

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Cisco Systems Inc.

Notified:  November 04, 2003 Updated:  November 04, 2003

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Hewlett-Packard Company

Notified:  November 04, 2003 Updated:  November 04, 2003

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Microsoft Corporation

Updated:  November 04, 2003

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

SuSE Inc.

Notified:  November 04, 2003 Updated:  November 04, 2003

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.


CVSS Metrics

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A

References

Acknowledgements

This vulnerability was discoverd by NISCC and Novell. Thanks to NISCC and OpenSSL for information used in this document.

This document was written by Art Manion.

Other Information

CVE IDs: CVE-2003-0851
Severity Metric: 3.23
Date Public: 2003-11-04
Date First Published: 2003-11-04
Date Last Updated: 2003-11-05 22:18 UTC
Document Revision: 20

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