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debiancveDebian Security Bug TrackerDEBIANCVE:CVE-2021-28689
HistoryJun 11, 2021 - 3:15 p.m.

CVE-2021-28689

2021-06-1115:15:00
Debian Security Bug Tracker
security-tracker.debian.org
9

5.5 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

2.1 Low

CVSS2

Access Vector

LOCAL

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

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

0.0004 Low

EPSS

Percentile

10.9%

x86: Speculative vulnerabilities with bare (non-shim) 32-bit PV guests 32-bit x86 PV guest kernels run in ring 1. At the time when Xen was developed, this area of the i386 architecture was rarely used, which is why Xen was able to use it to implement paravirtualisation, Xen’s novel approach to virtualization. In AMD64, Xen had to use a different implementation approach, so Xen does not use ring 1 to support 64-bit guests. With the focus now being on 64-bit systems, and the availability of explicit hardware support for virtualization, fixing speculation issues in ring 1 is not a priority for processor companies. Indirect Branch Restricted Speculation (IBRS) is an architectural x86 extension put together to combat speculative execution sidechannel attacks, including Spectre v2. It was retrofitted in microcode to existing CPUs. For more details on Spectre v2, see: http://xenbits.xen.org/xsa/advisory-254.html However, IBRS does not architecturally protect ring 0 from predictions learnt in ring 1. For more details, see: https://software.intel.com/security-software-guidance/deep-dives/deep-dive-indirect-branch-restricted-speculation Similar situations may exist with other mitigations for other kinds of speculative execution attacks. The situation is quite likely to be similar for speculative execution attacks which have yet to be discovered, disclosed, or mitigated.

OSVersionArchitecturePackageVersionFilename
Debian12allxen<= 4.17.3+10-g091466ba55-1~deb12u1xen_4.17.3+10-g091466ba55-1~deb12u1_all.deb
Debian11allxen<= 4.14.6-1xen_4.14.6-1_all.deb
Debian10allxen<= 4.11.4+107-gef32c7afa2-1xen_4.11.4+107-gef32c7afa2-1_all.deb
Debian999allxen<= 4.17.3+36-g54dacb5c02-1xen_4.17.3+36-g54dacb5c02-1_all.deb
Debian13allxen<= 4.17.3+10-g091466ba55-1xen_4.17.3+10-g091466ba55-1_all.deb

5.5 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

2.1 Low

CVSS2

Access Vector

LOCAL

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

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

0.0004 Low

EPSS

Percentile

10.9%

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