{"id":"CVE-2020-25603","state":"PUBLISHED","title":"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 lockl","description":"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.","publishedAt":"2020-09-23T21:34:56.000Z","updatedAt":"2024-08-04T15:33:05.752Z","severity":null,"assigner":"mitre","products":["n/a n/a"],"affected":[{"vendor":"n/a","product":"n/a","versions":[{"version":"n/a","status":"affected"}]}],"references":["https://xenbits.xen.org/xsa/advisory-340.html","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4JRXMKEMQRQYWYEPHVBIWUEAVQ3LU4FN/","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DA633Y3G5KX7MKRN4PFEGM3IVTJMBEOM/","https://www.debian.org/security/2020/dsa-4769","http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00008.html","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RJZERRBJN6E6STDCHT4JHP4MI6TKBCJE/","https://security.gentoo.org/glsa/202011-06"],"weaknesses":[],"ingestedAt":"2026-10-29T19:47:05.429Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2020/25xxx/CVE-2020-25603.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2020-25603","state":"PUBLISHED","datePublished":"2020-09-23T21:34:56.000Z","dateUpdated":"2024-08-04T15:33:05.752Z","assignerShortName":"mitre","assignerOrgId":"8254265b-2729-46b6-b9e3-3dfca2d5bfca","dateReserved":"2020-09-16T00:00:00.000Z"},"containers":{"cna":{"descriptions":[{"lang":"en","value":"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":[{"vendor":"n/a","product":"n/a","versions":[{"version":"n/a","status":"affected"}]}],"references":[{"url":"https://xenbits.xen.org/xsa/advisory-340.html","tags":["x_refsource_MISC"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4JRXMKEMQRQYWYEPHVBIWUEAVQ3LU4FN/","name":"FEDORA-2020-306b84fd07","tags":["vendor-advisory","x_refsource_FEDORA"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DA633Y3G5KX7MKRN4PFEGM3IVTJMBEOM/","name":"FEDORA-2020-f668e579be","tags":["vendor-advisory","x_refsource_FEDORA"]},{"url":"https://www.debian.org/security/2020/dsa-4769","name":"DSA-4769","tags":["vendor-advisory","x_refsource_DEBIAN"]},{"url":"http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00008.html","name":"openSUSE-SU-2020:1608","tags":["vendor-advisory","x_refsource_SUSE"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RJZERRBJN6E6STDCHT4JHP4MI6TKBCJE/","name":"FEDORA-2020-d46fe34349","tags":["vendor-advisory","x_refsource_FEDORA"]},{"url":"https://security.gentoo.org/glsa/202011-06","name":"GLSA-202011-06","tags":["vendor-advisory","x_refsource_GENTOO"]}],"problemTypes":[{"descriptions":[{"description":"n/a","lang":"en","type":"text"}]}],"providerMetadata":{"shortName":"mitre","dateUpdated":"2020-11-11T05:06:30.000Z","orgId":"8254265b-2729-46b6-b9e3-3dfca2d5bfca"},"x_legacyV4Record":{"CVE_data_meta":{"ASSIGNER":"cve@mitre.org","ID":"CVE-2020-25603","STATE":"PUBLIC"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"n/a","version":{"version_data":[{"version_value":"n/a"}]}}]},"vendor_name":"n/a"}]}},"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"An issue was discovered in Xen through 4.14.x. 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Arm systems will also be vulnerable if the CPU is able to re-order memory access. 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