Bug 1880137 (CVE-2020-25596) - CVE-2020-25596 xen: x86 pv guest kernel DoS via SYSENTER (XSA-339)
Summary: CVE-2020-25596 xen: x86 pv guest kernel DoS via SYSENTER (XSA-339)
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2020-25596
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1881617
Blocks: 1877386
TreeView+ depends on / blocked
 
Reported: 2020-09-17 18:26 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 19:14 UTC (History)
25 users (show)

Fixed In Version:
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Doc Text:
A flaw was found in Xen. One of Xen's sanitization paths injects a #GP fault and incorrectly delivers it twice to the guest. This flaw allows malicious or buggy user space to crash the guest kernel, resulting in a VM denial of service.
Clone Of:
Environment:
Last Closed: 2020-09-22 20:41:38 UTC
Embargoed:

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Description Guilherme de Almeida Suckevicz 2020-09-17 18:26:21 UTC 
The SYSENTER instruction leaves various state sanitization activities to software. One of Xen's sanitization paths injects a #GP fault, and incorrectly delivers it twice to the guest. This causes the guest kernel to observe a kernel-privilege #GP fault (typically fatal) rather than a user-privilege #GP fault (usually converted into SIGSEGV/etc).
Comment 1 Guilherme de Almeida Suckevicz 2020-09-17 18:26:27 UTC 
Acknowledgments:

Name: the Xen project
Comment 3 Mauro Matteo Cascella 2020-09-18 16:15:11 UTC 
Mitigation:

Running only x86 PVH/HVM guests avoids the vulnerability.
Comment 4 Mauro Matteo Cascella 2020-09-22 18:27:27 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1881617]
Comment 5 Product Security DevOps Team 2020-09-22 20:41:38 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2020-25596
Comment 6 Mauro Matteo Cascella 2020-09-23 07:37:03 UTC 
External References:

https://xenbits.xen.org/xsa/advisory-339.html
Comment 7 RaTasha Tillery-Smith 2020-09-29 19:15:40 UTC 
Statement:

All Xen versions from 3.2 onward are vulnerable. Red Hat Enterprise Linux 5 is not affected by this flaw, as it shipped in an older version of Xen.
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