Bug 1983720 (CVE-2021-36222) - CVE-2021-36222 krb5: Sending a request containing PA-ENCRYPTED-CHALLENGE padata element without using FAST could result in NULL dereference in KDC which leads to DoS
Summary: CVE-2021-36222 krb5: Sending a request containing PA-ENCRYPTED-CHALLENGE pada...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2021-36222
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: 1983728 1983729 1983733 1992011
Blocks: 1983721
TreeView+ depends on / blocked
 
Reported: 2021-07-19 15:27 UTC by Michael Kaplan
Modified: 2022-04-17 21:30 UTC (History)
51 users (show)

Fixed In Version: krb5 1.19.2
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in krb5. This flaw allows an unauthenticated attacker to cause a NULL dereference in the KDC by sending a request containing a PA-ENCRYPTED-CHALLENGE padata element without using FAST. The highest threat from this vulnerability is to system availability.
Clone Of:
Environment:
Last Closed: 2021-09-21 12:26:21 UTC
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:3576 0 None None None 2021-09-21 08:39:18 UTC

Description Michael Kaplan 2021-07-19 15:27:58 UTC 
In MIT krb5 releases 1.16 and later, an unauthenticated attacker can cause a null dereference in the KDC by sending a request containing a PA-ENCRYPTED-CHALLENGE padata element without using FAST.
Comment 1 Michael Kaplan 2021-07-19 15:32:23 UTC 
Fixed in fedora: https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/thread/CCCYLGJLCVVNJVOQKUGKXR2SNQIPFBFS/
Comment 2 Michael Kaplan 2021-07-19 15:34:44 UTC 
References: 

https://github.com/krb5/krb5/commit/fc98f520caefff2e5ee9a0026fdf5109944b3562
Comment 7 Marco Benatto 2021-08-10 14:31:03 UTC 
On ec_verify() function, when armor key is NULL it should return ENOENT, however due to a logic error the return value is overwritten by 0 in case k5memdup0() call is executed successfully before the check for armor key is executed. This leads to a NULL pointer dereference when further handling the armor key.
An attacker may leverage this by sending crafted requests to KDC server, leading it to crash and causing a DoS.
Comment 8 Marco Benatto 2021-08-10 14:33:26 UTC 
Created krb5 tracking bugs for this issue:

Affects: fedora-all [bug 1992011]
Comment 9 errata-xmlrpc 2021-09-21 08:39:14 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:3576 https://access.redhat.com/errata/RHSA-2021:3576
Comment 10 Product Security DevOps Team 2021-09-21 12:26:21 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-36222
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