{"schema_version":"1.7.5","id":"UBUNTU-CVE-2020-25603","published":"2020-09-23T22:15:00Z","modified":"2026-04-22T12:35:00.420334Z","related":["USN-5617-1"],"upstream":["CVE-2020-25603"],"details":"An issue was discovered in Xen through 4.14.x. There are missing memory barriers when accessing/allocating an event channel. Event channels control structures can be accessed lockless as long as the port is considered to be valid. Such a sequence is missing an appropriate memory barrier (e.g., smp_*mb()) to prevent both the compiler and CPU from re-ordering access. A malicious guest may be able to cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded. Systems running all versions of Xen are affected. Whether a system is vulnerable will depend on the CPU and compiler used to build Xen. For all systems, the presence and the scope of the vulnerability depend on the precise re-ordering performed by the compiler used to build Xen. We have not been able to survey compilers; consequently we cannot say which compiler(s) might produce vulnerable code (with which code generation options). GCC documentation clearly suggests that re-ordering is possible. Arm systems will also be vulnerable if the CPU is able to re-order memory access. Please consult your CPU vendor. x86 systems are only vulnerable if a compiler performs re-ordering.","affected":[{"package":{"name":"xen","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/xen@4.6.5-0ubuntu1.4?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.5.1-0ubuntu1","4.5.1-0ubuntu2","4.6.0-1ubuntu1","4.6.0-1ubuntu2","4.6.0-1ubuntu4","4.6.0-1ubuntu4.1","4.6.0-1ubuntu4.2","4.6.0-1ubuntu4.3","4.6.5-0ubuntu1","4.6.5-0ubuntu1.1","4.6.5-0ubuntu1.2","4.6.5-0ubuntu1.4"],"ecosystem_specific":{"binaries":[{"binary_name":"libxen-4.6","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"libxenstore3.0","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.4-amd64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.4-arm64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.4-armhf","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.5-amd64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.5-arm64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.5-armhf","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.6-amd64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.6-arm64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-hypervisor-4.6-armhf","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-system-amd64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-system-arm64","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-system-armhf","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-utils-4.6","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xen-utils-common","binary_version":"4.6.5-0ubuntu1.4"},{"binary_name":"xenstore-utils","binary_version":"4.6.5-0ubuntu1.4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2020/UBUNTU-CVE-2020-25603.json"}},{"package":{"name":"xen","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/xen@4.9.2-0ubuntu1?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.9.0-0ubuntu3","4.9.0-0ubuntu4","4.9.2-0ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"libxen-4.9","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"libxenstore3.0","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.6-amd64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.6-arm64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.6-armhf","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.7-amd64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.7-arm64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.7-armhf","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.8-amd64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.8-arm64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.8-armhf","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.9-amd64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.9-arm64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-hypervisor-4.9-armhf","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-system-amd64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-system-arm64","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-system-armhf","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-utils-4.9","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xen-utils-common","binary_version":"4.9.2-0ubuntu1"},{"binary_name":"xenstore-utils","binary_version":"4.9.2-0ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2020/UBUNTU-CVE-2020-25603.json"}},{"package":{"name":"xen","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/xen@4.11.3+24-g14b62ab3e5-1ubuntu2.3?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.11.3+24-g14b62ab3e5-1ubuntu2.3"}]}],"versions":["4.9.2-0ubuntu2","4.9.2-0ubuntu6","4.9.2-0ubuntu7","4.11.3+24-g14b62ab3e5-1ubuntu1","4.11.3+24-g14b62ab3e5-1ubuntu2","4.11.3+24-g14b62ab3e5-1ubuntu2.2"],"ecosystem_specific":{"availability":"No 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