high
7.8
CWE
670
Advisory Published
Updated

CVE-2020-25603

First published: Wed Sep 23 2020(Updated: )

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.

Credit: cve@mitre.org cve@mitre.org

Affected SoftwareAffected VersionHow to fix
Xen Xen<=4.14.0
Fedoraproject Fedora=31
Fedoraproject Fedora=32
Fedoraproject Fedora=33
openSUSE Leap=15.2
Debian Debian Linux=10.0
debian/xen
4.14.6-1
4.14.5+94-ge49571868d-1
4.17.3+10-g091466ba55-1~deb12u1
4.17.3+36-g54dacb5c02-1

Remedy

https://xenbits.xen.org/xsa/advisory-340.html

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Reference Links

Frequently Asked Questions

  • What is CVE-2020-25603?

    CVE-2020-25603 is a vulnerability in Xen through 4.14.x that involves missing memory barriers when accessing/allocating an event channel.

  • What is the severity of CVE-2020-25603?

    The severity of CVE-2020-25603 has not been specified.

  • How does CVE-2020-25603 affect Xen?

    CVE-2020-25603 affects Xen through 4.14.x by allowing unauthorized access to event channel control structures.

  • What is the recommended remedy for CVE-2020-25603?

    The recommended remedy for CVE-2020-25603 is to update Xen to version 4.11.3+24- or apply the specific patches provided by the respective package sources.

  • Where can I find more information about CVE-2020-25603?

    More information about CVE-2020-25603 can be found at the following references: [Advisory-340](https://xenbits.xen.org/xsa/advisory-340.html), [Fedora Update 1](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4JRXMKEMQRQYWYEPHVBIWUEAVQ3LU4FN/), [Fedora Update 2](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DA633Y3G5KX7MKRN4PFEGM3IVTJMBEOM/)

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