XenSource Xen 4.4 on 32-bit PV Guest L3 Pagetable mm.c get_page_from_l3e access control

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7.8$0-$5k0.00

Summaryinfo

A vulnerability categorized as problematic has been discovered in XenSource Xen 4.4 on 32-bit PV Guest. This impacts the function get_page_from_l3e of the file mm.c of the component L3 Pagetable. The manipulation results in access control. This vulnerability is identified as CVE-2016-7092. The attack is only possible with local access. There is not any exploit available. A patch should be applied to remediate this issue.

Detailsinfo

A vulnerability classified as critical has been found in XenSource Xen 4.4 on 32-bit PV Guest (Virtualization Software). Affected is the function get_page_from_l3e of the file mm.c of the component L3 Pagetable. The manipulation with an unknown input leads to a access control vulnerability. CWE is classifying the issue as CWE-264. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

The get_page_from_l3e function in arch/x86/mm.c in Xen allows local 32-bit PV guest OS administrators to gain host OS privileges via vectors related to L3 recursive pagetables.

The weakness was released 09/08/2016 by Jeremie Boutoille as XSA-185 as confirmed security advisory (Website). The advisory is available at xenbits.xen.org. This vulnerability is traded as CVE-2016-7092 since 08/25/2016. The exploitability is told to be easy. Local access is required to approach this attack. The successful exploitation needs a authentication. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1068 by the MITRE ATT&CK project. The reason for this vulnerability is this part of code: 

if ( unlikely(rc == -EINVAL) && get_l3_linear_pagetable(l3e, pfn, d) )
The advisory points out:
On real hardware, a 32-bit PAE guest must leave the USER and RW bit clear in L3 pagetable entries, but the pagetable walk behaves as if they were set. (The L3 entries are cached in processor registers, and don't actually form part of the pagewalk.) When running a 32-bit PV guest on a 64-bit Xen, Xen must always OR in the USER and RW bits for L3 updates for the guest to observe architectural behaviour. This is unsafe in combination with recursive pagetables.

The vulnerability scanner Nessus provides a plugin with the ID 93413 (Debian DLA-614-1 : xen security update), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Debian Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 169239 (SUSE Enterprise Linux Security Update for xen (SUSE-SU-2016:2473-1)).

Applying a patch is able to eliminate this problem. The bugfix is ready for download at xenbits.xen.org. A possible mitigation has been published immediately after the disclosure of the vulnerability. The vulnerability will be addressed with the following lines of code:

if ( unlikely(rc == -EINVAL) &&
   !is_pv_32bit_domain(d) &&
   get_l3_linear_pagetable(l3e, pfn, d) )

The vulnerability is also documented in the databases at Tenable (93413), SecurityFocus (BID 92862†) and SecurityTracker (ID 1036751†). Entries connected to this vulnerability are available at VDB-90368, VDB-91387, VDB-91388 and VDB-91389. If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.2
VulDB Meta Temp Score: 8.0

VulDB Base Score: 8.2
VulDB Temp Score: 7.8
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 8.2
NVD Vector: 🔍

CVSSv2info

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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Access control
CWE: CWE-264
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: No

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 93413
Nessus Name: Debian DLA-614-1 : xen security update
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 900325
OpenVAS Name: Fedora Update for xen FEDORA-2016-7d2c67d1f5
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

Interest: 🔍
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Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Patch: xenbits.xen.org

Timelineinfo

08/25/2016 🔍
09/08/2016 +14 days 🔍
09/08/2016 +0 days 🔍
09/08/2016 +0 days 🔍
09/08/2016 +0 days 🔍
09/09/2016 +1 days 🔍
09/12/2016 +3 days 🔍
09/21/2016 +9 days 🔍
04/12/2019 +933 days 🔍

Sourcesinfo

Vendor: citrix.com

Advisory: XSA-185
Researcher: Jeremie Boutoille
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2016-7092 (🔍)
GCVE (CVE): GCVE-0-2016-7092
GCVE (VulDB): GCVE-100-91386

OVAL: 🔍

SecurityFocus: 92862 - Xen CVE-2016-7092 Local Privilege Escalation Vulnerability
SecurityTracker: 1036751

See also: 🔍

Entryinfo

Created: 09/09/2016 09:21
Updated: 04/12/2019 10:25
Changes: 09/09/2016 09:21 (80), 04/12/2019 10:25 (12)
Complete: 🔍
Cache ID: 216:2A5:103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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