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AUSCERT External Security Bulletin Redistribution
ESB-2020.2681.2
GRUB2 Arbitrary Code Execution Vulnerability
11 August 2020
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Cloud Services Router 1000V Series
Cisco Integrated Services Virtual Router (ISRv)
Cisco Identity Services Engine (ISE)
Cisco Enterprise NFV Infrastructure Software (NFVIS)
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Root Compromise -- Existing Account
Execute Arbitrary Code/Commands -- Existing Account
Increased Privileges -- Existing Account
Modify Arbitrary Files -- Existing Account
Denial of Service -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2020-10713
Reference: ASB-2020.0136
ASB-2020.0135
ESB-2020.2647
ESB-2020.2616
ESB-2020.2590
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-grub2-code-exec-xLePCAPY
Revision History: August 11 2020: Updated to v1.1 of advisory
August 6 2020: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
RUB2 Arbitrary Code Execution Vulnerability
Priority: High
Advisory ID: cisco-sa-grub2-code-exec-xLePCAPY
First Published: 2020 August 4 23:00 GMT
Last Updated: 2020 August 10 15:49 GMT
Version 1.1: Interim
Workarounds: No workarounds available
CVE-2020-10713
CWE-119
Summary
o On July 29, 2020, a research paper titled "There's a Hole in the Boot" was
made publicly available. This paper discusses a vulnerability discovered in
the GRand Unified Bootloader version 2 (GRUB2) bootloader that may allow an
attacker to execute arbitrary code at system boot time.
The vulnerability is due to incorrect bounds checking of certain values
parsed from the GRUB2 configuration file. An attacker could exploit this
vulnerability by supplying a crafted configuration file for GRUB2. When
this file is processed, an exploitable buffer overflow condition may occur.
A successful exploit could allow the attacker to inject arbitrary code that
is executed before the operating system is loaded on the targeted system.
On systems protected by the Unified Extensible Firmware Interface (UEFI)
secure boot feature, exploitation of this vulnerability may allow the
attacker to tamper with the secure boot process.
Multiple Cisco products are affected by this vulnerability.
Cisco will release software updates that address this vulnerability. Any
workarounds for a specific Cisco product or service will be documented in
the relevant Cisco bugs, which are identified in the Vulnerable Products
section of this advisory.
This advisory will be updated as additional information becomes available.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-grub2-code-exec-xLePCAPY
Affected Products
o The following table lists Cisco products that are affected by the
vulnerability that is described in this advisory.
The Vulnerable Products section includes Cisco bug IDs for each affected
product or service. The bugs are accessible through the Cisco Bug Search
Tool and contain additional platform-specific information, including
workarounds (if available) and fixed software releases.
Any product or service not listed in the Products Under Investigation or
Vulnerable Products section of this advisory is to be considered not
vulnerable. Because this is an ongoing investigation, please be aware that
products and services that are currently considered not vulnerable may
subsequently be considered vulnerable as additional information becomes
available.
Vulnerable Products
This vulnerability affects Cisco Products if they implement a vulnerable
release of the GRUB2 bootloader and do not validate the GRUB2 configuration
file.
The following table lists Cisco products that are affected by the
vulnerability that is described in this advisory. If a future release date
is indicated for software, the date provided represents an estimate based
on all information known to Cisco as of the Last Updated date at the top of
the advisory. Availability dates are subject to change based on a number of
factors, including satisfactory testing results and delivery of other
priority features and fixes. If no version or date is listed for an
affected component (indicated by a blank field and/or an advisory
designation of Interim), Cisco is continuing to evaluate the fix and will
update the advisory as additional information becomes available. After the
advisory is marked Final, customers should refer to the associated Cisco
bug(s) for further details.
Product Cisco Bug Fixed Release
ID Availability
Routing and Switching - Enterprise and Service Provider
Cisco Cloud Services Router 1000V Series CSCvv04959
Cisco Integrated Services Virtual Router CSCvv04959
(ISRv)
Network and Content Security Devices
Cisco Identity Services Engine (ISE) CSCvv04957
Unified Computing
Cisco Enterprise NFV Infrastructure CSCvv05161
Software (NFVIS)
Products Confirmed Not Vulnerable
Only products and services listed in the Vulnerable Products section of
this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following
products and services.
Network and Content Security Devices
Cisco Firepower Management System
Routing and Switching - Enterprise and Service Provider
Cisco 1000 Series Connected Grid Routers
Cisco IR800 Series Integrated Services Routers (ISRs)
Details
o This vulnerability affects Cisco devices that integrate a vulnerable
release of the GRUB2 bootloader. The bootloader is software that is
executed during the system startup process; it is initialized by the system
firmware and performs the necessary initialization for loading the
operating system. GRUB2 reads its configuration parameters from a text
file. An affected version of GRUB2 improperly performs the bounds checking
of specific values parsed from the configuration file.
An attacker who can modify this configuration file (by possessing either
administrative privileges to the device or physical access to the targeted
system) could exploit this vulnerability by supplying a crafted
configuration file for GRUB2. When this file is processed, a heap-based
buffer overflow may occur. The attacker could use this vulnerability to
achieve arbitrary code execution in the preboot environment of an affected
system.
Exploitation of this vulnerability would require an attacker to modify the
GRUB2 configuration file. Most Cisco devices validate the GRUB2
configuration file during the boot process. An attempt to exploit this
vulnerability will cause the digital signature check to fail. When this
check fails, the Cisco device will not let that software boot, thereby
preventing the malicious code from running.
On a subset of Cisco devices, the GRUB2 configuration file is not
validated. These products are affected by the vulnerability described in
this advisory, and listed in Vulnerable Products section.
Workarounds
o Any workarounds for a specific Cisco product or service will be documented
in the relevant Cisco bugs, which are identified in the Vulnerable Products
section of this advisory.
Fixed Software
o For information about fixed software releases , consult the Cisco bugs
identified in the Vulnerable Products section of this advisory.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories page , to determine exposure and a complete
upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is aware that
proof-of-concept exploit code is available for the vulnerability described
in this advisory.
The Cisco PSIRT is not aware of any malicious use of the vulnerability that
is described in this advisory.
Source
o Cisco would like to thank Mickey Shkatov and Jesse Michael of Eclypsium for
reporting this vulnerability.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-grub2-code-exec-xLePCAPY
Revision History
o +---------+----------------------------+----------+---------+-------------+
| Version | Description | Section | Status | Date |
+---------+----------------------------+----------+---------+-------------+
| | Updated the summary and | Summary, | | |
| 1.1 | moved the product under | Affected | Interim | 2020-AUG-10 |
| | investigation to the list | Products | | |
| | of vulnerable products. | | | |
+---------+----------------------------+----------+---------+-------------+
| 1.0 | Initial public release. | - | Interim | 2020-AUG-04 |
+---------+----------------------------+----------+---------+-------------+
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