CVE-2017-7995 : What You Need to Know
Learn about CVE-2017-7995, a vulnerability in Xen PV guests before version 4.3 allowing unauthorized memory access, potentially leading to information disclosure. Find mitigation steps and best practices for long-term security.
Xen PV guests before version 4.3 had a vulnerability that allowed unauthorized access to MMIO ranges, potentially leading to information disclosure.
Understanding CVE-2017-7995
What is CVE-2017-7995?
In versions of Xen prior to 4.3, Xen PV guests would verify access permissions to MMIO ranges only after accessing them. This could result in host PCI device space memory reads, leading to the disclosure of information.
The Impact of CVE-2017-7995
This vulnerability could allow attackers to access sensitive information from the host system through unauthorized memory reads.
Technical Details of CVE-2017-7995
Vulnerability Description
The get_user function in Xen PV guests before version 4.3 did not properly check access permissions to MMIO ranges, allowing unauthorized memory reads.
Affected Systems and Versions
- Xen versions before 4.3
- Note: Upstream Xen Project no longer supports versions before 4.5.x
Exploitation Mechanism
Attackers could exploit this vulnerability by accessing MMIO ranges in Xen PV guests before proper permission verification, leading to potential information disclosure.
Mitigation and Prevention
Immediate Steps to Take
- Upgrade Xen to version 4.3 or later to mitigate this vulnerability
- Monitor and restrict access to sensitive memory areas
Long-Term Security Practices
- Regularly update and patch Xen to the latest supported version
- Implement access controls and monitoring mechanisms to prevent unauthorized memory access
Patching and Updates
- Apply security patches provided by Xen Project to address this vulnerability