Debian Security Advisory

DSA-2129-1 krb5 -- checksum verification weakness

Date Reported:
01 Dec 2010
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2010-1323.
More information:

A vulnerability has been found in krb5, the MIT implementation of Kerberos.

MIT krb5 clients incorrectly accept unkeyed checksums in the SAM-2 preauthentication challenge: an unauthenticated remote attacker could alter a SAM-2 challenge, affecting the prompt text seen by the user or the kind of response sent to the KDC. Under some circumstances, this can negate the incremental security benefit of using a single-use authentication mechanism token.

MIT krb5 incorrectly accepts RFC 3961 key-derivation checksums using RC4 keys when verifying KRB-SAFE messages: an unauthenticated remote attacker has a 1/256 chance of forging KRB-SAFE messages in an application protocol if the targeted pre-existing session uses an RC4 session key. Few application protocols use KRB-SAFE messages.

The Common Vulnerabilities and Exposures project has assigned CVE-2010-1323 to these issues.

For the stable distribution (lenny), these problems have been fixed in version 1.6.dfsg.4~beta1-5lenny6.

The builds for the mips architecture are not included in this advisory. They will be released as soon as they are available.

For the testing distribution (squeeze) and the unstable distribution (sid), these problem have been fixed in version 1.8.3+dfsg-3.

We recommend that you upgrade your krb5 packages.

Fixed in:

Debian GNU/Linux 5.0 (lenny)

Architecture-independent component:
HP Precision:
Intel IA-32:
Intel IA-64:
Little-endian MIPS:
IBM S/390:
Sun Sparc:

MD5 checksums of the listed files are available in the original advisory.