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paul

Advisories MDVSA-2010:246: krb5

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Multiple vulnerabilities were discovered and corrected in krb5:

 

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. 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 (CVE-2010-1323).

 

An unauthenticated remote attacker can forge GSS tokens that

are intended to be integrity-protected but unencrypted, if the

targeted pre-existing application session uses a DES session key. An

authenticated remote attacker can forge PACs if using a KDC that does

not filter client-provided PAC data. This can result in privilege

escalation against a service that relies on PAC contents to make

authorization decisions. An unauthenticated remote attacker has a 1/256

chance of swapping a client-issued KrbFastReq into a different KDC-REQ,

if the armor key is RC4. The consequences are believed to be minor

(CVE-2010-1324).

 

An authenticated remote attacker that controls a legitimate service

principal has a 1/256 chance of forging the AD-SIGNEDPATH signature

if the TGT key is RC4, allowing it to use self-generated evidence

tickets for S4U2Proxy, instead of tickets obtained from the user or

with S4U2Self. Configurations using RC4 for the TGT key are believed

to be rare. An authenticated remote attacker has a 1/256 chance of

forging AD-KDC-ISSUED signatures on authdata elements in tickets

having an RC4 service key, resulting in privilege escalation against

a service that relies on these signatures. There are no known uses

of the KDC-ISSUED authdata container at this time (CVE-2010-4020.

 

An authenticated remote attacker that controls a legitimate service

principal could obtain a valid service ticket to itself containing

valid KDC-generated authorization data for a client whose TGS-REQ

it has intercepted. The attacker could then use this ticket for

S4U2Proxy to impersonate the targeted client even if the client never

authenticated to the subverted service. The vulnerable configuration

is believed to be rare (CVE-2010-4021).

 

The updated packages have been patched to correct this issue.

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