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debiancveDebian Security Bug TrackerDEBIANCVE:CVE-2020-29566
HistoryDec 15, 2020 - 5:15 p.m.

CVE-2020-29566

2020-12-1517:15:14
Debian Security Bug Tracker
security-tracker.debian.org
18
xen
dos
stack overflow
x86
hvm guests
device model

CVSS2

4.9

Attack Vector

LOCAL

Attack Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

COMPLETE

AV:L/AC:L/Au:N/C:N/I:N/A:C

CVSS3

5.5

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

0.001

Percentile

19.0%

An issue was discovered in Xen through 4.14.x. When they require assistance from the device model, x86 HVM guests must be temporarily de-scheduled. The device model will signal Xen when it has completed its operation, via an event channel, so that the relevant vCPU is rescheduled. If the device model were to signal Xen without having actually completed the operation, the de-schedule / re-schedule cycle would repeat. If, in addition, Xen is resignalled very quickly, the re-schedule may occur before the de-schedule was fully complete, triggering a shortcut. This potentially repeating process uses ordinary recursive function calls, and thus could result in a stack overflow. A malicious or buggy stubdomain serving a HVM guest can cause Xen to crash, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are affected. Arm systems are not affected. Only x86 stubdomains serving HVM guests can exploit the vulnerability.

OSVersionArchitecturePackageVersionFilename
Debian12allxen< 4.14.0+88-g1d1d1f5391-1xen_4.14.0+88-g1d1d1f5391-1_all.deb
Debian11allxen< 4.14.0+88-g1d1d1f5391-1xen_4.14.0+88-g1d1d1f5391-1_all.deb
Debian999allxen< 4.14.0+88-g1d1d1f5391-1xen_4.14.0+88-g1d1d1f5391-1_all.deb
Debian13allxen< 4.14.0+88-g1d1d1f5391-1xen_4.14.0+88-g1d1d1f5391-1_all.deb

CVSS2

4.9

Attack Vector

LOCAL

Attack Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

COMPLETE

AV:L/AC:L/Au:N/C:N/I:N/A:C

CVSS3

5.5

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

0.001

Percentile

19.0%