Bug 1844166 (CVE-2020-11086)

Summary:	CVE-2020-11086 freerdp: out-of-bounds read in ntlm_read_ntlm_v2_client_challenge function
Product:	[Other] Security Response	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	mads, negativo17, oholy, pahan
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	freerdp 2.1.0	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2020-09-29 22:01:36 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1844167, 1844168, 1844169, 1844170, 1844535, 1844536
Bug Blocks:	1844196

Description Guilherme de Almeida Suckevicz 2020-06-04 18:15:21 UTC

In FreeRDP less than or equal to 2.0.0, there is an out-of-bound read in ntlm_read_ntlm_v2_client_challenge that reads up to 28 bytes out-of-bound to an internal structure. This has been fixed in 2.1.0.

Reference:
https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-fg8v-w34r-c974

Upstream commit:
https://github.com/FreeRDP/FreeRDP/commit/c098f21fdaadca57ff649eee1674f6cc321a2ec4

Comment 1 Guilherme de Almeida Suckevicz 2020-06-04 18:15:48 UTC

Created freerdp tracking bugs for this issue:

Affects: epel-6 [bug 1844168]
Affects: fedora-all [bug 1844167]


Created freerdp1.2 tracking bugs for this issue:

Affects: epel-7 [bug 1844170]
Affects: fedora-all [bug 1844169]

Comment 2 Todd Cullum 2020-06-05 01:24:28 UTC

Technical Summary:

In the NTLM challenge/response code which is used in freerdp client and server, there was no remaining length check of the stream before reading NTLM challenge data from it.

ntlm_read_ntlm_v2_client_challenge() and ntlm_read_ntlm_v2_response() from winpr/libwinpr/sspi/NTLM/ntlm_compute.c are both affected in freerdp version 2.0.0-rc4 shipped in Red Hat Enterprise Linux 7 and Red Hat Enterprise Linux 8. freerdp 1.0.2,  shipped with Red Hat Enterprise Linux 6 is not affected by this flaw. The patch uses Stream_GetRemainingLength() to ensure that the stream buffer is not over-read.

Comment 4 Todd Cullum 2020-06-05 01:44:03 UTC

Note - the metadata on the upstream advisory[1] could be confusing because the title refers to ntlm_read_ntlm_v2_response(), while the impact description refers to ntlm_read_ntlm_v2_client_challenge(). The description seems to be associated with the bug in ntlm_read_ntlm_v2_client_challenge(), rather than ntlm_read_ntlm_v2_response(). I did not see a further check implemented in ntlm_read_ntlm_v2_response().

1. https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-fg8v-w34r-c974

Comment 9 Todd Cullum 2020-06-05 16:17:10 UTC

Mitigation:

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Comment 10 errata-xmlrpc 2020-09-29 20:44:03 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2020:4031 https://access.redhat.com/errata/RHSA-2020:4031

Comment 11 Product Security DevOps Team 2020-09-29 22:01:36 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-2020-11086

Comment 12 errata-xmlrpc 2020-11-04 02:39:04 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2020:4647 https://access.redhat.com/errata/RHSA-2020:4647