MITKRB5-SA-2010-002 denial of service in SPNEGO [CVE-2010-0628 VU#839413]

2010-03-2500:00:00

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MITKRB5-SA-2010-002

MIT krb5 Security Advisory 2010-002
Original release: 2010-03-23
Last update: 2010-03-23

Topic: denial of service in SPNEGO

CVE-2010-0628
VU#839413
denial of service in SPNEGO

CVSSv2 Vector: AV:N/AC:L/Au:N/C:N/I:N/A:C/E:POC/RL:OF/RC:C

CVSSv2 Base Score: 7.8

Access Vector: Network
Access Complexity: Low
Authentication: None
Confidentiality Impact: None
Integrity Impact: None
Availability Impact: Complete

CVSSv2 Temporal Score: 6.1

Exploitability: Proof-of-Concept
Remediation Level: Official Fix
Report Confidence: Confirmed

SUMMARY

In MIT krb5 releases krb5-1.7 and later, the SPNEGO GSS-API mechanism
can experience an assertion failure when receiving certain invalid
messages. This can cause a GSS-API application to crash.

This is an implementation vulnerability in MIT krb5, and not a
vulnerability in the Kerberos protocol.

IMPACT

An unauthenticated remote attacker could cause a GSS-API application,
including the Kerberos administration daemon (kadmind) to crash.

AFFECTED SOFTWARE

kadmind in MIT releases krb5-1.7 and later
FTP daemon in MIT releases krb5-1.7 and later
Third-party software using the GSS-API library from MIT krb5
releases krb5-1.7 and later
MIT releases prior to krb5-1.7 did not contain the vulnerable code.

FIXES

The upcoming krb5-1.7.2 and krb5-1.8.1 releases will contain fixes
for this vulnerability.
Apply the patch available at

http://web.mit.edu/kerberos/advisories/2010-002-patch.txt

A PGP-signed patch is available at

http://web.mit.edu/kerberos/advisories/2010-002-patch.txt.asc

REFERENCES

This announcement is posted at:

http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2010-002.txt

This announcement and related security advisories may be found on the
MIT Kerberos security advisory page at:

    http://web.mit.edu/kerberos/advisories/index.html

The main MIT Kerberos web page is at:

    http://web.mit.edu/kerberos/index.html

CVSSv2:

http://www.first.org/cvss/cvss-guide.html
http://nvd.nist.gov/cvss.cfm?calculator&amp;adv&amp;version=2

CVE: CVE-2010-0628
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-0628

CERT: VU#839413
http://www.kb.cert.org/vuls/id/839413

ACKNOWLEDGMENTS

Thanks to Nalin Dahyabhai, Jan iankko Lieskovsky, and Zbysek Mraz (all
from Red Hat) for discovering and reporting this vulnerability.

CONTACT

The MIT Kerberos Team security contact address is
<[email protected]>. When sending sensitive information,
please PGP-encrypt it using the following key:

pub 2048R/8B8DF501 2010-01-15 [expires: 2011-02-01]
uid MIT Kerberos Team Security Contact <[email protected]>

DETAILS

A patch to fix CVE-2009-0845 interacted poorly with new functionality
introduced in krb5-1.7. This allowed an error condition to occur
where receiving an invalid packet could cause an assertion failure,
crashing the program and causing denial of service.

When the spnego_gss_accept_sec_context() function (in
src/lib/gssapi/spnego/spnego_mech.c) receives an invalid packet during
the beginning of a GSS-API protocol exchange, it can set some internal
state that tells it to send an error token without first creating a
context handle, but some subsequently executed code contains a call to
assert() that requires that the context handle be non-null.