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CVE-2021-28706

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB...

8.6 HighFix available

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

2.23%Up 1.8 points since Nov 24, 2021

What each source reports

NVD Score used8.6

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: CVE-2021-28706
CVSS 3.1: 8.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CVSS 2.0: 7.8 HighAV:N/AC:L/Au:N/C:N/I:N/A:C
Weakness: CWE-770
Updated: 2026-11-02

CVE ListNo score

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: CVE-2021-28706
Updated: 2026-11-02

EUVDEUVD-2021-15363No score

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: EUVD-2021-15363
Updated: 2026-11-03

GitHub AdvisoriesGHSA-x89c-76jf-xx4h8.6

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB...

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: GHSA-x89c-76jf-xx4h
CVSS 3.1: 8.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Weakness: CWE-770
Updated: 2026-11-02

OSVALPINE-CVE-2021-287068.6

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: ALPINE-CVE-2021-28706
CVSS 3.1: 8.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Updated: 2026-11-02

OSV8.6

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: CVE-2021-28706
CVSS 3.1: 8.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Updated: 2026-11-02

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OSVDEBIAN-CVE-2021-287068.6

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: DEBIAN-CVE-2021-28706
CVSS 3.1: 8.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-287068.6

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Record: UBUNTU-CVE-2021-28706
CVSS 3.1: 8.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Updated: 2026-11-02

OSVopenSUSE-SU-2021:1543-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28702: Fixed PCI devices with RMRRs not deassigned correctly (XSA-386) (bsc#1191363).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Update to Xen 4.13.4 bug fix release (bsc#1027519).

This update was imported from the SUSE:SLE-15-SP2:Update update project.

Record: openSUSE-SU-2021:1543-1
Updated: 2026-11-02

OSVopenSUSE-SU-2021:3968-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28702: Fixed PCI devices with RMRRs not deassigned correctly (XSA-386) (bsc#1191363).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Update to Xen 4.14.3 bug fix release (bsc#1027519).

Record: openSUSE-SU-2021:3968-1
Updated: 2026-11-02

OSVSUSE-SU-2021:14848-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-0089: Fixed Speculative Code Store Bypass (XSA-375) (bsc#1186433).
CVE-2021-20255: Fixed stack overflow via infinite recursion in eepro100 (bsc#1182654).
CVE-2021-28690: Fixed x86 TSX Async Abort protections not restored after S3 (XSA-377) (bsc#1186434).
CVE-2021-28692: Fixed inappropriate x86 IOMMU timeout detection / handling (XSA-373) (bsc#1186429).
CVE-2021-28697: Fixed grant table v2 status pages may remain accessible after de-allocation (XSA-379) (bsc#1189376).
CVE-2021-28698: Fixed long running loops in grant table handling. (XSA-380) (bsc#1189378).
CVE-2021-28701: Fixed race condition in XENMAPSPACE_grant_table handling (XSA-384) (bsc#1189632).
CVE-2021-28703: Fixed grant table v2 status pages may remain accessible after de-allocation (take two) (XSA-387) (bsc#1192555).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
CVE-2021-3527: Fixed unbounded stack allocation in usbredir (bsc#1186013).
CVE-2021-3592: Fixed invalid pointer initialization may lead to information disclosure in slirp (bootp) (bsc#1187369).
CVE-2021-3594: Fixed invalid pointer initialization may lead to information disclosure in slirp (udp) (bsc#1187378).
CVE-2021-3595: Fixed invalid pointer initialization may lead to information disclosure in slirp (tftp) (bsc#1187376).
CVE-2021-3682: Fixed free call on invalid pointer in usbredir bufp_alloc (bsc#1189150).
CVE-2021-3930: Fixed off-by-one error in mode_sense_page() in hw/scsi/scsi-disk.c (bsc#1192526).

Record: SUSE-SU-2021:14848-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3813-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).

Record: SUSE-SU-2021:3813-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3842-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28701: Fixed race condition in XENMAPSPACE_grant_table handling (XSA-384) (bsc#1189632).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Integrate bugfixes (bsc#1189373, bsc#1189378).

Record: SUSE-SU-2021:3842-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3849-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28701: Fixed race condition in XENMAPSPACE_grant_table handling (XSA-384) (bsc#1189632).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Integrate bugfixes (bsc#1189373, bsc#1189378)

Record: SUSE-SU-2021:3849-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3851-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).

Record: SUSE-SU-2021:3851-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3852-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28702: Fixed PCI devices with RMRRs not deassigned correctly (XSA-386) (bsc#1191363).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Fixed 15sp4 uefi fv guest on 12sp5 host unable to bootup with sriov pci device plugin (bsc#1191510).
Upstream bug fixes (bsc#1027519).

Record: SUSE-SU-2021:3852-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3888-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28702: Fixed PCI devices with RMRRs not deassigned correctly (XSA-386) (bsc#1191363).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Update to Xen 4.13.4 bug fix release (bsc#1027519).

Record: SUSE-SU-2021:3888-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3968-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28702: Fixed PCI devices with RMRRs not deassigned correctly (XSA-386) (bsc#1191363).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Update to Xen 4.14.3 bug fix release (bsc#1027519).

Record: SUSE-SU-2021:3968-1
Updated: 2026-11-02

OSVSUSE-SU-2021:3977-1No score

Security update for xen

This update for xen fixes the following issues:

CVE-2021-28701: Fixed race condition in XENMAPSPACE_grant_table handling (XSA-384) (bsc#1189632).
CVE-2021-28702: Fixed PCI devices with RMRRs not deassigned correctly (XSA-386) (bsc#1191363).
CVE-2021-28704, CVE-2021-28707, CVE-2021-28708: Fixed PoD operations on misaligned GFNs (XSA-388) (bsc#1192557).
CVE-2021-28705, CVE-2021-28709: Fixed issues with partially successful P2M updates on x86 (XSA-389) (bsc#1192559).
CVE-2021-28706: Fixed guests may exceed their designated memory limit (XSA-385) (bsc#1192554).
Upstream bug fixes (bsc#1027519)

Record: SUSE-SU-2021:3977-1
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`xen` Alpine:v3.11	3.2 up to 4.13.4-r2	4.13.4-r2
`xen` Alpine:v3.12	3.2 up to 4.13.4-r2	4.13.4-r24.13.4-r3
`xen` Alpine:v3.13	3.2 up to 4.14.5-r0	4.14.5-r0
`xen` Alpine:v3.14	3.2 up to 4.15.2-r0	4.15.2-r0
`xen` Alpine:v3.15	3.2 up to 4.15.2-r0	4.15.2-r0
`xen` Debian:12	before 4.14.3+32-g9de3671772-1	4.14.3+32-g9de3671772-1
`xen` Debian:13	before 4.14.3+32-g9de3671772-1	4.14.3+32-g9de3671772-1
`xen` Debian:14	before 4.14.3+32-g9de3671772-1	4.14.3+32-g9de3671772-1
`xen` Debian:11 From an advisory covering 7 CVEs	before 4.14.3+32-g9de3671772-1~deb11u1, plus listed versions 4.14.2+25-gb6a8c4f72d-24.14.3-14.14.3-1~deb11u1	4.14.3+32-g9de3671772-1~deb11u1
`xen` SUSE:Linux Enterprise Server 11 SP4-LTSS From an advisory covering 17 CVEs	before 4.4.4_50-61.67.1	4.4.4_50-61.67.1

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Affected packages
Package	Affected	Fixed
`xen` SUSE:Linux Enterprise Server 12 SP2-BCL From an advisory covering 6 CVEs	before 4.7.6_18-43.82.1	4.7.6_18-43.82.1
`xen` SUSE:Linux Enterprise High Performance Computing 15-ESPOS From an advisory covering 7 CVEs	before 4.10.4_30-3.68.1	4.10.4_30-3.68.1
`xen` SUSE:Linux Enterprise High Performance Computing 15-LTSS From an advisory covering 7 CVEs	before 4.10.4_30-3.68.1	4.10.4_30-3.68.1
`xen` SUSE:Linux Enterprise Server for SAP Applications 15 From an advisory covering 7 CVEs	before 4.10.4_30-3.68.1	4.10.4_30-3.68.1
`xen` SUSE:OpenStack Cloud 9 From an advisory covering 7 CVEs	before 4.11.4_24-2.65.1	4.11.4_24-2.65.1
`xen` SUSE:OpenStack Cloud Crowbar 9 From an advisory covering 7 CVEs	before 4.11.4_24-2.65.1	4.11.4_24-2.65.1
`xen` SUSE:Linux Enterprise Server for SAP Applications 12 SP4 From an advisory covering 7 CVEs	before 4.11.4_24-2.65.1	4.11.4_24-2.65.1
`xen` SUSE:Linux Enterprise Server 12 SP4-LTSS From an advisory covering 7 CVEs	before 4.11.4_24-2.65.1	4.11.4_24-2.65.1
`xen` SUSE:HPE Helion OpenStack 8 From an advisory covering 6 CVEs	before 4.9.4_24-3.97.1	4.9.4_24-3.97.1
`xen` SUSE:OpenStack Cloud 8 From an advisory covering 6 CVEs	before 4.9.4_24-3.97.1	4.9.4_24-3.97.1
`xen` SUSE:OpenStack Cloud Crowbar 8 From an advisory covering 6 CVEs	before 4.9.4_24-3.97.1	4.9.4_24-3.97.1
`xen` SUSE:Linux Enterprise Server for SAP Applications 12 SP3 From an advisory covering 6 CVEs	before 4.9.4_24-3.97.1	4.9.4_24-3.97.1
`xen` SUSE:Linux Enterprise Server 12 SP3-LTSS From an advisory covering 6 CVEs	before 4.9.4_24-3.97.1	4.9.4_24-3.97.1
`xen` SUSE:Linux Enterprise Server 12 SP3-BCL From an advisory covering 6 CVEs	before 4.9.4_24-3.97.1	4.9.4_24-3.97.1
`xen` SUSE:Linux Enterprise Software Development Kit 12 SP5 From an advisory covering 7 CVEs	before 4.12.4_16-3.55.1	4.12.4_16-3.55.1
`xen` SUSE:Linux Enterprise Server 12 SP5 From an advisory covering 7 CVEs	before 4.12.4_16-3.55.1	4.12.4_16-3.55.1
`xen` SUSE:Linux Enterprise Server for SAP Applications 12 SP5 From an advisory covering 7 CVEs	before 4.12.4_16-3.55.1	4.12.4_16-3.55.1
`xen` SUSE:Linux Enterprise Module for Basesystem 15 SP2 From an advisory covering 7 CVEs	before 4.13.4_02-3.40.1	4.13.4_02-3.40.1
`xen` SUSE:Linux Enterprise Module for Server Applications 15 SP2 From an advisory covering 7 CVEs	before 4.13.4_02-3.40.1	4.13.4_02-3.40.1
`xen` SUSE:Linux Enterprise Micro 5.0 From an advisory covering 7 CVEs	before 4.13.4_02-3.40.1	4.13.4_02-3.40.1
`xen` SUSE:Linux Enterprise Module for Basesystem 15 SP3 From an advisory covering 7 CVEs	before 4.14.3_04-3.15.1	4.14.3_04-3.15.1
`xen` SUSE:Linux Enterprise Module for Server Applications 15 SP3 From an advisory covering 7 CVEs	before 4.14.3_04-3.15.1	4.14.3_04-3.15.1
`xen` SUSE:Linux Enterprise Micro 5.1 From an advisory covering 7 CVEs	before 4.14.3_04-3.15.1	4.14.3_04-3.15.1
`xen` SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS From an advisory covering 8 CVEs	before 4.12.4_16-3.57.1	4.12.4_16-3.57.1
`xen` SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSS From an advisory covering 8 CVEs	before 4.12.4_16-3.57.1	4.12.4_16-3.57.1
`xen` SUSE:Linux Enterprise Server 15 SP1-BCL From an advisory covering 8 CVEs	before 4.12.4_16-3.57.1	4.12.4_16-3.57.1
`xen` SUSE:Linux Enterprise Server 15 SP1-LTSS From an advisory covering 8 CVEs	before 4.12.4_16-3.57.1	4.12.4_16-3.57.1
`xen` SUSE:Linux Enterprise Server for SAP Applications 15 SP1 From an advisory covering 8 CVEs	before 4.12.4_16-3.57.1	4.12.4_16-3.57.1
`xen` SUSE:Enterprise Storage 6 From an advisory covering 8 CVEs	before 4.12.4_16-3.57.1	4.12.4_16-3.57.1
`xen` Ubuntu:16.04:LTS	All versions, plus listed versions 4.5.1-0ubuntu14.5.1-0ubuntu24.6.0-1ubuntu14.6.0-1ubuntu24.6.0-1ubuntu4 Show 7 moreShow less 4.6.0-1ubuntu4.14.6.0-1ubuntu4.24.6.0-1ubuntu4.34.6.5-0ubuntu14.6.5-0ubuntu1.14.6.5-0ubuntu1.24.6.5-0ubuntu1.4	None known
`xen` Ubuntu:18.04:LTS	All versions, plus listed versions 4.9.0-0ubuntu34.9.0-0ubuntu44.9.2-0ubuntu1	None known
`xen` Ubuntu:20.04:LTS	All versions, plus listed versions 4.9.2-0ubuntu24.9.2-0ubuntu64.9.2-0ubuntu74.11.3+24-g14b62ab3e5-1ubuntu14.11.3+24-g14b62ab3e5-1ubuntu24.11.3+24-g14b62ab3e5-1ubuntu2.24.11.3+24-g14b62ab3e5-1ubuntu2.3	None known
`xen` Ubuntu:22.04:LTS	All versions, plus listed versions 4.11.4+24-gddaaccbbab-1ubuntu24.16.0-1~ubuntu24.16.0-1~ubuntu2.1	None known
`xen` Ubuntu:24.04:LTS	All versions, plus listed versions 4.17.2-14.17.2+55-g0b56bed864-14.17.2+76-ge1f9cb16e2-14.17.2+76-ge1f9cb16e2-1ubuntu14.17.3+10-g091466ba55-14.17.3+10-g091466ba55-1.1ubuntu24.17.3+10-g091466ba55-1.1ubuntu3	None known
`xen` Ubuntu:25.10	All versions, plus listed versions 4.20.0-1ubuntu14.20.0+68-g35cb38b222-1	None known
`xen` Ubuntu:26.10	All versions, plus listed versions 4.20.2+7-g1badcf5035-2build24.20.2+37-g61ff35323e-1ubuntu14.20.3+127-gc42374a105-1	None known
`xen` Ubuntu:26.04:LTS	All versions, plus listed versions 4.20.0+68-g35cb38b222-14.20.2+7-g1badcf5035-24.20.2+7-g1badcf5035-2build2	None known
`xen` openSUSE:Leap 15.2 From an advisory covering 7 CVEs	before 4.13.4_02-lp152.2.33.1	4.13.4_02-lp152.2.33.1
`xen` openSUSE:Leap 15.3 From an advisory covering 7 CVEs	before 4.14.3_04-3.15.1	4.14.3_04-3.15.1

History

History
Recorded	Changed	Sources
Nov 6, 2026	affected, facts
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-28706 is a high vulnerability (CVSS 8.6) in Debian Linux, published November 24, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.23%, the 83rd percentile. Fixed in xen 4.13.4-r2.

References

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