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TITLE:
Kerberos Multiple Vulnerabilities

SECUNIA ADVISORY ID:
SA42396

VERIFY ADVISORY:
Secunia.com
http://secunia.com/advisories/42396/
Customer Area (Credentials Required)
https://ca.secunia.com/?page=viewadvisory&vuln_id=42396

RELEASE DATE:
2010-12-02

DISCUSS ADVISORY:
http://secunia.com/advisories/42396/#comments

AVAILABLE ON SITE AND IN CUSTOMER AREA:
 * Last Update
 * Popularity
 * Comments
 * Criticality Level
 * Impact
 * Where
 * Solution Status
 * Operating System / Software
 * CVE Reference(s)

http://secunia.com/advisories/42396/

ONLY AVAILABLE IN CUSTOMER AREA:
 * Authentication Level
 * Report Reliability
 * Secunia PoC
 * Secunia Analysis
 * Systems Affected
 * Approve Distribution
 * Remediation Status
 * Secunia CVSS Score
 * CVSS

https://ca.secunia.com/?page=viewadvisory&vuln_id=42396

ONLY AVAILABLE WITH SECUNIA CSI AND SECUNIA PSI:
 * AUTOMATED SCANNING

http://secunia.com/vulnerability_scanning/personal/
http://secunia.com/vulnerability_scanning/corporate/wsus_sccm_3rd_third_party_patching/

DESCRIPTION:
Some vulnerabilities have been reported in Kerberos, which can be
exploited by malicious users and malicious people to conduct spoofing
attacks and bypass certain security features.

1) The krb5 GSS-API applications do not properly validate the
checksums of DES session keys for version 2 (RFC 4121) of the GSS-API
krb5 mechanism, which can be exploited to forge unencrypted but
integrity protected GSS tokens.

Successful exploitation requires that the pre-existing application
session uses a DES session key.

This vulnerability affects krb-1.7 or newer.

2) The krb5 application services do not properly verify the checksum
of PAC signatures, which can be exploited to e.g. gain escalated
privileges by forging the PACs.

Successful exploitation requires that the attacker is authenticated
and that the KDC in use does not filter client-provided PAC data but
e.g. makes authorisation decisions based on the PAC content.

This vulnerability affects krb-1.7 or newer. Systems exclusively
running krb5-1.8 block the attack.

3) The MIT krb5 KDC incorrectly accepts RFC 3961 key-derivation
checksums when verifying the req-checksum in KrbFastArmoredReqs,
which can be exploited to e.g. swap a client-issued KrbFastReq into a
different KDC-REQ.

Successful exploitation requires that the armor key in use is RC4.

This vulnerability affects krb-1.7 or newer.

4) The MIT krb5 clients incorrectly accept unkeyed checksums in the
SAM-2 preauthentication challenges, which can be exploited to e.g.
forge the prompt text or change the response sent to the KDC.

This vulnerability affects krb5-1.3 or newer.

5) The MIT krb5 incorrectly accepts RFC 3961 key-derivation checksums
when verifying KRB-SAFE messages, which can be exploited to forge
KRB-SAFE messages.

Successful exploitation requires that the pre-existing application
session uses an RC4 session key.

This vulnerability affects krb5-1.3 or newer.

6) The MIT krb5 incorrectly accepts RFC 3961 key-derivation checksums
when verifying AD-SIGNEDPATH authorisation data, which can be
exploited to forge the AD-SIGNEDPATH signature and e.g. self-generate
"evidence" tickets for S4U2Proxy.

Successful exploitation requires that the attacker is authenticated
and controls a legitimate service principal and that the TGT key is
RC4.

This vulnerability affects krb5-1.8 or newer.

7) The MIT krb5 incorrectly accepts RFC 3961 key-derivation checksums
when verifying AD-KDC-ISSUED authorisation data, which can be
exploited to forge AD-KDC-ISSUED signatures on authdata elements.

Successful exploitation requires that the attacker is authenticated
and that the tickets have an RC4 service key.

This vulnerability affects krb5-1.8 or newer.

SOLUTION:
Apply patches.

Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

PROVIDED AND/OR DISCOVERED BY:
Reported by the vendor.

ORIGINAL ADVISORY:
MITKRB5-SA-2010-007:
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2010-007.txt

OTHER REFERENCES:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

DEEP LINKS:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

EXTENDED DESCRIPTION:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

EXTENDED SOLUTION:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

EXPLOIT:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

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About:
This Advisory was delivered by Secunia as a free service to help
private users keeping their systems up to date against the latest
vulnerabilities.

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Please Note:
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Secunia NEVER sends attached files with advisories.
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use those supplied by the vendor.

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