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NVD / CVE Program· CNA Linux

CVE-2023-53663: KVM: nSVM: Check instead of asserting on nested TSC scaling support

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.14% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 02b24270568f65dd607c4a848512dc8055b4491b, 6c1ecfea1daf6e75c46e295aad99dfbafd878897, 7cafe9b8e22bb3d77f130c461aedf6868c4aaf58.

Low priority for now. Upgrade to Linux Linux 02b24270568f65dd607c4a848512dc8055b4491b, 6c1ecfea1daf6e75c46e295aad99dfbafd878897, 7cafe9b8e22bb3d77f130c461aedf6868c4aaf58 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: KVM: nSVM: Check instead of asserting on nested TSC scaling support Check for nested TSC scaling support on nested SVM VMRUN instead of asserting that TSC scaling is exposed to L1 if L1's MSR_AMD64_TSC_RATIO has diverged from KVM's default. Userspace can trigger the WARN at will by writing the MSR and then updating guest CPUID to hide the feature (modifying guest CPUID is allowed anytime before KVM_RUN). E.g. hacking KVM's state_test selftest to do vcpu_set_msr(vcpu, MSR_AMD64_TSC_RATIO, 0); vcpu_clear_cpuid_feature(vcpu, X86_FEATURE_TSCRATEMSR); after restoring state in a new VM+vCPU yields an endless supply of: ------------[ cut here ]------------ WARNING: CPU: 164 PID: 62565 at arch/x86/kvm/svm/nested.c:699 nested_vmcb02_prepare_control+0x3d6/0x3f0 [kvm_amd] Call Trace: <TASK> enter_svm_guest_mode+0x114/0x560 [kvm_amd] nested_svm_vmrun+0x260/0x330 [kvm_amd] vmrun_interception+0x29/0x30 [kvm_amd] svm_invoke_exit_handler+0x35/0x100 [kvm_amd] svm_handle_exit+0xe7/0x180 [kvm_amd] kvm_arch_vcpu_ioctl_run+0x1eab/0x2570 [kvm] kvm_vcpu_ioctl+0x4c9/0x5b0 [kvm] __se_sys_ioctl+0x7a/0xc0 __x64_sys_ioctl+0x21/0x30 do_syscall_64+0x41/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x45ca1b Note, the nested #VMEXIT path has the same flaw, but needs a different fix and will be handled separately.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Oct 7, 2025
Updated
Jun 17, 2026
EPSS
0.1% · 3th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.16 and later · before 6.1.54
  • linux linux kernel6.2 and later · before 6.5.4

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.16affected
    • 5228eb96a4875f8cf5d61d486e3795ac14df8904 and later · before 6c1ecfea1daf6e75c46e295aad99dfbafd878897affected · git
    • 5228eb96a4875f8cf5d61d486e3795ac14df8904 and later · before 02b24270568f65dd607c4a848512dc8055b4491baffected · git
    • 5228eb96a4875f8cf5d61d486e3795ac14df8904 and later · before 7cafe9b8e22bb3d77f130c461aedf6868c4aaf58affected · git
    • before 5.16not affected · semver
    • 6.1.54 and later · up to and including 6.1.*not affected · semver
    • 6.5.4 and later · up to and including 6.5.*not affected · semver
    • 6.6 and laternot affected · original_commit_for_fix

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.55-16.1.55-1
Debian:13linuxbefore 6.5.6-16.5.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2023-53661Oct 7, 2025 · bnxt: avoid overflow in bnxt_get_nvram_directory()
    22Monitor
  • ← EarlierCVE-2023-53662Oct 7, 2025 · ext4: fix memory leaks in ext4_fname_{setup_filename,prepare_lookup}
    22Monitor
  • Later →CVE-2023-53664Oct 7, 2025 · OPP: Fix potential null ptr dereference in dev_pm_opp_get_required_pstate()
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux02b24270568f65dd607c4a848512dc8055b4491bVendor (CNA)
Linux Linux6c1ecfea1daf6e75c46e295aad99dfbafd878897Vendor (CNA)
Linux Linux7cafe9b8e22bb3d77f130c461aedf6868c4aaf58Vendor (CNA)
debian:linux6.1.55-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records