CVE-2023-46841

x86: shadow stack vs exceptions from emulation stubs

Published Mar 20, 2024 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Description
Recent x86 CPUs offer functionality named Control-flow Enforcement
Technology (CET). A sub-feature of this are Shadow Stacks (CET-SS).
CET-SS is a hardware feature designed to protect against Return Oriented
Programming attacks. When enabled, traditional stacks holding both data
and return addresses are accompanied by so called "shadow stacks",
holding little more than return addresses. Shadow stacks aren't
writable by normal instructions, and upon function returns their
contents are used to check for possible manipulation of a return address
coming from the traditional stack.

In particular certain memory accesses need intercepting by Xen. In
various cases the necessary emulation involves kind of replaying of
the instruction. Such replaying typically involves filling and then
invoking of a stub. Such a replayed instruction may raise an
exceptions, which is expected and dealt with accordingly.

Unfortunately the interaction of both of the above wasn't right:
Recovery involves removal of a call frame from the (traditional) stack.
The counterpart of this operation for the shadow stack was missing.

Remediation

Vendor Workaround

While in principle it is possible to disable use of CET on capable systems using the "cet=no-shstk" command line option, doing so disables an important security feature and may therefore not be advisable.

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-5836-1 xen security update
EUVD EUVD EUVD-2023-51007 Recent x86 CPUs offer functionality named Control-flow Enforcement Technology (CET). A sub-feature of this are Shadow Stacks (CET-SS). CET-SS is a hardware feature designed to protect against Return Oriented Programming attacks. When enabled, traditional stacks holding both data and return addresses are accompanied by so called "shadow stacks", holding little more than return addresses. Shadow stacks aren't writable by normal instructions, and upon function returns their contents are used to check for possible manipulation of a return address coming from the traditional stack. In particular certain memory accesses need intercepting by Xen. In various cases the necessary emulation involves kind of replaying of the instruction. Such replaying typically involves filling and then invoking of a stub. Such a replayed instruction may raise an exceptions, which is expected and dealt with accordingly. Unfortunately the interaction of both of the above wasn't right: Recovery involves removal of a call frame from the (traditional) stack. The counterpart of this operation for the shadow stack was missing.
History
Type Values Removed Values Added
First Time appeared Fedoraproject
Fedoraproject fedora
Xen
Xen xen
Weaknesses NVD-CWE-Other
CPEs cpe:2.3:o:fedoraproject:fedora:40:*:*:*:*:*:*:*
cpe:2.3:o:xen:xen:*:*:*:*:*:*:x86:*
Vendors & Products Fedoraproject
Fedoraproject fedora
Xen
Xen xen
Type Values Removed Values Added
Description Recent x86 CPUs offer functionality named Control-flow Enforcement Technology (CET). A sub-feature of this are Shadow Stacks (CET-SS). CET-SS is a hardware feature designed to protect against Return Oriented Programming attacks. When enabled, traditional stacks holding both data and return addresses are accompanied by so called "shadow stacks", holding little more than return addresses. Shadow stacks aren't writable by normal instructions, and upon function returns their contents are used to check for possible manipulation of a return address coming from the traditional stack. In particular certain memory accesses need intercepting by Xen. In various cases the necessary emulation involves kind of replaying of the instruction. Such replaying typically involves filling and then invoking of a stub. Such a replayed instruction may raise an exceptions, which is expected and dealt with accordingly. Unfortunately the interaction of both of the above wasn't right: Recovery involves removal of a call frame from the (traditional) stack. The counterpart of this operation for the shadow stack was missing. Recent x86 CPUs offer functionality named Control-flow Enforcement Technology (CET). A sub-feature of this are Shadow Stacks (CET-SS). CET-SS is a hardware feature designed to protect against Return Oriented Programming attacks. When enabled, traditional stacks holding both data and return addresses are accompanied by so called "shadow stacks", holding little more than return addresses. Shadow stacks aren't writable by normal instructions, and upon function returns their contents are used to check for possible manipulation of a return address coming from the traditional stack. In particular certain memory accesses need intercepting by Xen. In various cases the necessary emulation involves kind of replaying of the instruction. Such replaying typically involves filling and then invoking of a stub. Such a replayed instruction may raise an exceptions, which is expected and dealt with accordingly. Unfortunately the interaction of both of the above wasn't right: Recovery involves removal of a call frame from the (traditional) stack. The counterpart of this operation for the shadow stack was missing.
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
XEN
Published
Updated
Nov 4, 2025, 6:18 PM
Reserved
Oct 27, 2023, 7:55 AM
Status
Modified
Published
Mar 20, 2024, 11:15 AM
Modified
Jun 17, 2026, 6:31 AM