[OpenSSL Advisory] Denial of Service in ASN.1 parsing

Type securityvulns
Reporter Securityvulns
Modified 2003-11-05T00:00:00



OpenSSL Security Advisory [4 November 2003]

Denial of Service in ASN.1 parsing

Previously, OpenSSL 0.9.6k was released on the 30 September 2003 to address various ASN.1 issues. The issues were found using a test suite from NISCC (www.niscc.gov.uk) and fixed by Dr Stephen Henson (steve@openssl.org) of the OpenSSL core team.

Subsequent to that release, Novell Inc. carried out further testing using the NISCC suite. They discovered that there was a denial of service vulnerability in OpenSSL version 0.9.6k when running on a Windows platform.

A bug in OpenSSL 0.9.6 would cause certain ASN.1 sequences to trigger a large recursion. On platforms such as Windows this large recursion cannot be handled correctly and so the bug causes OpenSSL to crash. A remote attacker could exploit this flaw if they can send arbitrary ASN.1 sequences which would cause OpenSSL to crash. This could be performed for example by sending a client certificate to a SSL/TLS enabled server which is configured to accept them.

We do not believe this issue could be exploited further than a Denial of Service attack.

Patches for this issue have been created by Dr Stephen Henson (steve@openssl.org) of the OpenSSL core team.

Who is affected?

OpenSSL 0.9.6k is affected by the bug, but the denial of service does not affect all platforms. This issue does not affect OpenSSL 0.9.7. Currently only OpenSSL running on Windows platforms is known to crash.


Upgrade to OpenSSL 0.9.6l or 0.9.7c. Recompile any OpenSSL applications statically linked to OpenSSL libraries.

OpenSSL 0.9.6l is available for download via HTTP and FTP from the following master locations (you can find the various FTP mirrors under http://www.openssl.org/source/mirror.html):

o http://www.openssl.org/source/
o ftp://ftp.openssl.org/source/

The distribution file name is:

o openssl-0.9.6l.tar.gz [normal]
  MD5 checksum: 843a65ddc56634f0e30a4f9474bb5b27
o openssl-engine-0.9.6l.tar.gz [engine]
  MD5 checksum: dd372198cdf31667f2cb29cd76fbda1c

The checksums were calculated using the following command:

openssl md5 < openssl-0.9.6l.tar.gz
openssl md5 < openssl-engine-0.9.6l.tar.gz


The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CAN-2003-0851 to this issue.


URL for this Security Advisory: http://www.openssl.org/news/secadv_20031104.txt -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux)

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