VulnerabilityAwaiting classification

CVE-2023-53996

CRITICAL · 9.3 CVSS v3.1 Published 2025-12-24

Mitigation only

No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.

See remediation →

98/100

Remediation priority · Urgent

No privileges Zero-click

Official description

NVD · unedited

In the Linux kernel, the following vulnerability has been resolved: x86/sev: Make enc_dec_hypercall() accept a size instead of npages enc_dec_hypercall() accepted a page count instead of a size, which forced its callers to round up. As a result, non-page aligned vaddrs caused pages to be spuriously marked as decrypted via the encryption status hypercall, which in turn caused consistent corruption of pages during live migration. Live migration requires accurate encryption status information to avoid migrating pages from the wrong perspective.

Technical summary

dbcve analysis · high confidence

In the Linux kernel's SEV (Secure Encrypted Virtualization) implementation, the enc_dec_hypercall() function incorrectly accepted a page count (npages) instead of a size parameter. This forced callers to round up to page boundaries, causing non-page-aligned virtual addresses to have their pages spuriously marked as decrypted via the encryption status hypercall. During live migration of SEV-encrypted VMs, this resulted in consistent memory corruption because pages were migrated with incorrect encryption status information.

MitigationApply the kernel patch that modifies enc_dec_hypercall() to accept a size parameter instead of npages, enabling accurate encryption status tracking for non-page-aligned addresses. Organizations using SEV live migration should prioritize this update.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown

From the vector

Attack vector: Local
Complexity: Low
Privileges: None
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

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

Am I affected?

dbcve checks

Work through these to decide whether this CVE applies to you.

Identify the running kernel version

Run `uname -r` or check `/proc/version` to get the exact kernel version string

Affected if The kernel version is older than the version containing the fix for enc_dec_hypercall() (approximately kernel 6.1-6.2 range depending on distribution) and the system uses AMD SEV
Verify AMD SEV hardware support exists

Check CPU flags by running `grep -o 'sev' /proc/cpuinfo` or use `cpuid | grep -i sev` to confirm the processor supports AMD SEV

Affected if The CPU does not report SEV support, then the system cannot be affected by this vulnerability
Confirm SEV is enabled in the kernel

Check kernel boot parameters in `/proc/cmdline` for 'sev' or 'sev-es', or check KVM module parameters via `cat /sys/module/kvm_amd/parameters/sev`

Affected if SEV is actively enabled in the kernel configuration and the kernel version is vulnerable
Identify running SEV-encrypted virtual machines

For each running VM, check its XML config via `virsh dumpxml <vmname>` for `<os><loader>...</loader></os>` or check memory encryption status with `ls -la /dev/sev` or `kvmstat` showing encrypted guests

Affected if SEV-encrypted VMs are running and live migration will be performed, exposing the system to potential data corruption during migration

A system is affected only if it runs a vulnerable Linux kernel version with AMD SEV support enabled and performs live migration of SEV-encrypted virtual machines.

Generated from the published advisory. Verify against your own configuration.

Remediation

From vendor data

Mitigation available No clean upgrade yet — mitigate in the meantime

Mitigation

Apply the kernel patch that modifies enc_dec_hypercall() to accept a size parameter instead of npages, enabling accurate encryption status tracking for non-page-aligned addresses. Organizations using SEV live migration should prioritize this update.

Have this fixed Scoped from the published advisory

Consultation2.0 h
Implementation4.0 h
Testing4.0 h
Review / QA2.0 h

12.0 hours of engineering $2,080

Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.

Scan for this in your stack

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References

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-53996 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2023-53996?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

A fix existsA vendor remedy is published

Severity 9.3 Critical

Exploit likelihood EPSS, next 30 days 0.1%

Remediation

A high-priority fix

Have this fixed 12 hrs · Moderate

Typical engagement from $2,080

Get a fix See the full breakdown ↓

A high-priority vulnerability. Send your environment and a specialist will scope CVE-2023-53996 and return a fixed quote and timeline.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

Check your environment

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

CVSS breakdown

Am I affected?

Remediation

References