Linux Foundation Xen up to 4.3.0 fbld Instruction Emulation correct information disclosure

CVSS Meta Temp Score
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3.2$0-$5k0.00

A vulnerability classified as problematic was found in Linux Foundation Xen (Virtualization Software). Affected by this vulnerability is an unknown part of the component fbld Instruction Emulation. The manipulation of the argument correct as part of a HVM Guest leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. The summary by CVE is:

The fbld instruction emulation in Xen 3.3.x through 4.3.x does not use the correct variable for the source effective address, which allows local HVM guests to obtain hypervisor stack information by reading the values used by the instruction.

The weakness was released 09/30/2013 by Jan Beulich with SuSE as XSA-66 as confirmed mailinglist post (oss-sec). It is possible to read the advisory at seclists.org. The public release was coordinated with Linux Foundation. This vulnerability is known as CVE-2013-4361 since 06/12/2013. Attacking locally is a requirement. A single authentication is necessary for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK. The advisory points out:

A malicious guest might be able to find out information about the contents of the hypervisor stack, by observing which values are actually being used by fbld and inferring what the address must have been. Depending on the actual values on the stack this attack might be very difficult to carry out.

The vulnerability scanner Nessus provides a plugin with the ID 70421 (Fedora 20 : xen-4.3.0-7.fc20 (2013-18300)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Fedora Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 370045 (Citrix XenServer Security Update (CTX139295)). The advisory illustrates:

Only HVM guests can take advantage of this vulnerability.

Applying the patch xsa66.patch is able to eliminate this problem. It is possible to mitigate the problem by applying the configuration setting PV Guests only. The best possible mitigation is suggested to be patching the affected component. A possible mitigation has been published immediately after the disclosure of the vulnerability. The mailinglist post contains the following remark:

Running only PV guests will avoid this issue. There is no mitigation available for HVM guests. We believe this vulnerability would require significant research to exploit.

The vulnerability is also documented in the vulnerability database at Tenable (70421). Additional details are provided at openwall.com. Entries connected to this vulnerability are available at 10532, 10533 and 10668.

Productinfo

Type

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB CVSS-B Score: 🔍
VulDB CVSS-BT Score: 🔍
VulDB Vector: 🔍
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CVSSv3info

VulDB Meta Base Score: 3.3
VulDB Meta Temp Score: 3.2

VulDB Base Score: 3.3
VulDB Temp Score: 3.2
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv2info

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

NVD Base Score: 🔍

Exploitinginfo

Class: Information disclosure
CWE: CWE-200 / CWE-284 / CWE-266
ATT&CK: T1592

Local: Yes
Remote: No

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 70421
Nessus Name: Fedora 20 : xen-4.3.0-7.fc20 (2013-18300)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 866990
OpenVAS Name: Fedora Update for xen FEDORA-2013-18373
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

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

Patch: xsa66.patch
Config: PV Guests only

Timelineinfo

06/12/2013 🔍
09/30/2013 +109 days 🔍
09/30/2013 +0 days 🔍
09/30/2013 +0 days 🔍
09/30/2013 +0 days 🔍
10/01/2013 +1 days 🔍
10/01/2013 +0 days 🔍
10/03/2013 +2 days 🔍
10/15/2013 +12 days 🔍
05/26/2021 +2780 days 🔍

Sourcesinfo

Vendor: linuxfoundation.org

Advisory: XSA-66
Researcher: Jan Beulich
Organization: SuSE
Status: Confirmed
Coordinated: 🔍

CVE: CVE-2013-4361 (🔍)
OVAL: 🔍

Vulnerability Center: 41676 - Xen 3.3 - 4.3 Information Leakage Through fbld Instruction Emulation, Low
SecurityFocus: 62709
OSVDB: 97954

Misc.: 🔍
See also: 🔍

Entryinfo

Created: 10/03/2013 11:49
Updated: 05/26/2021 06:40
Changes: 10/03/2013 11:49 (80), 06/25/2018 09:18 (7), 05/26/2021 06:40 (4)
Complete: 🔍

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