Bug 1771366 (CVE-2019-18420) - CVE-2019-18420 xen: allows guest OS users to cause denial of service via VCPUOP_initialise hypercall
Summary: CVE-2019-18420 xen: allows guest OS users to cause denial of service via VCPU...
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2019-18420
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1771368
Blocks: 1771369
TreeView+ depends on / blocked
 
Reported: 2019-11-12 09:14 UTC by Dhananjay Arunesh
Modified: 2020-02-18 17:58 UTC (History)
23 users (show)

Fixed In Version:
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Last Closed: 2020-02-18 17:58:51 UTC


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Description Dhananjay Arunesh 2019-11-12 09:14:15 UTC
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOP_initialise hypercall. hypercall_create_continuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format character was done using BUG(), which crashes Xen. One path, via the VCPUOP_initialise hypercall, has a bad format character. The BUG() can be hit if VCPUOP_initialise executes for a sufficiently long period of time for a continuation to be created. Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only x86 PV guests can exploit the vulnerability. HVM and PVH guests, and guests on ARM systems, cannot exploit the vulnerability.

Reference:
http://www.openwall.com/lists/oss-security/2019/10/31/1

Comment 1 Dhananjay Arunesh 2019-11-12 09:15:12 UTC
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1771368]

Comment 2 Dhananjay Arunesh 2019-11-12 09:15:51 UTC
External References:

http://xenbits.xen.org/xsa/advisory-296.html


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