Bug 1485510 (CVE-2017-7562) - CVE-2017-7562 krb5: Authentication bypass by improper validation of certificate EKU and SAN
Summary: CVE-2017-7562 krb5: Authentication bypass by improper validation of certifica...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2017-7562
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1498767
Blocks: 1485513 1498774
TreeView+ depends on / blocked
 
Reported: 2017-08-25 22:00 UTC by Pedro Sampaio
Modified: 2019-09-29 14:19 UTC (History)
39 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
An authentication bypass flaw was found in the way krb5's certauth interface handled the validation of client certificates. A remote attacker able to communicate with the KDC could potentially use this flaw to impersonate arbitrary principals under rare and erroneous circumstances.
Clone Of:
Environment:
Last Closed: 2019-06-08 03:22:16 UTC
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2018:0666 0 None None None 2018-04-10 08:03:08 UTC

Description Pedro Sampaio 2017-08-25 22:00:29 UTC 
A flaw was found in krb5 certificate EKU validation which could lead to improper authorization if a forged certificate with the right EKU and no SAN is used.

The PKINIT certauth eku module should never authoritatively authorize
a certificate, because an extended key usage does not establish a
relationship between the certificate and any specific user; it only
establishes that the certificate was created for PKINIT client
authentication.

Upstream bug:

https://github.com/krb5/krb5/pull/694

Upstream patch:

https://github.com/krb5/krb5/pull/694/commits/50fe4074f188c2d4da0c421e96553acea8378db2
https://github.com/krb5/krb5/pull/694/commits/1de6ca2f2eb1fdbab51f1549a25a6903aefcc196
https://github.com/krb5/krb5/pull/694/commits/b7af544e50a4d8291524f590e20dd44430bf627d
Comment 7 errata-xmlrpc 2018-04-10 08:02:54 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2018:0666 https://access.redhat.com/errata/RHSA-2018:0666
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