dbcve.org
Epyc 7763 FirmwareOperating system · Amd

CVE-2021-26339

MEDIUM · 5.5 CVSS v3.1 Published 2022-05-11
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

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.

NVD · unedited
A bug in AMD CPU’s core logic may allow for an attacker, using specific code from an unprivileged VM, to trigger a CPU core hang resulting in a potential denial of service. AMD believes the specific code includes a specific x86 instruction sequence that would not be generated by compilers.

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.

dbcve analysis · moderate confidence

A hardware bug in AMD CPU core logic allows an unprivileged VM to trigger a CPU core hang using a specific, manually-crafted x86 instruction sequence (not compiler-generated), resulting in denial of service. The vulnerability is in the CPU silicon itself, requiring a microcode or firmware update from AMD.

MitigationApply AMD CPU firmware/microcode updates as they become available. Cloud providers should ensure host systems receive AMD microcode updates. Virtualization administrators may need to implement CPU scheduling mitigations or migrate affected workloads to patched hosts.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Epyc 7763 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7713p FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7713 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7663 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7643 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 75f3 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7543p FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7543 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7

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.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

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.

dbcve checks

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

  1. Identify the CPU model
    Run 'lscpu' or 'cat /proc/cpuinfo' and look for the Model name field. Confirm it is an AMD Epyc 7003 series (Milan) processor such as Epyc 7763, 7713p, 7713, 7663, 7643, 75f3, 7543p, or 7543.
    Affected if The CPU is not an AMD Epyc 7003 (Milan) series processor from the list, then the system is not affected by this specific CVE.
  2. Check the current firmware version
    Check the host BIOS/firmware version using 'dmidecode -s bios-version' or check the vendor-specific firmware string via 'dmesg | grep -i microcode' or '/proc/cpuinfo' microcode field. Look for the firmware version string.
    Affected if The firmware version cannot be determined or is not visible, treat it as potentially vulnerable and consult the system vendor for the milanpi-sp3 firmware version.
  3. Compare firmware version against the threshold
    Compare the installed firmware version string to 'milanpi-sp3_1.0.0.7'. Versions earlier than this (such as milanpi-sp3_1.0.0.5 or earlier) are within the affected range.
    Affected if The firmware version is lower than milanpi-sp3_1.0.0.7, then the system is affected and vulnerable to CPU core hang attacks from unprivileged VMs.
  4. Verify virtualization is in use
    Check if the host is running a hypervisor or if VMs are present. Run 'systemd-detect-virt' or check for hypervisor flags in '/proc/cpuinfo' (flags containing 'hypervisor').
    Affected if The host does not run any virtualization and no VMs are present, the specific attack vector of an unprivileged VM causing CPU hang does not apply, though the hardware flaw still exists in the silicon.

The system is affected if it runs an AMD Epyc 7003 (Milan) processor with firmware version lower than milanpi-sp3_1.0.0.7, particularly in virtualized environments where untrusted VMs can execute x86 instructions.

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

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply AMD CPU firmware/microcode updates as they become available. Cloud providers should ensure host systems receive AMD microcode updates. Virtualization administrators may need to implement CPU scheduling mitigations or migrate affected workloads to patched hosts.

Recommended fix High confidence

milanpi-sp3_1.0.0.7

  1. Obtain the updated firmware (milanpi-sp3_1.0.0.7 or later) from the AMD website or your system manufacturer
  2. Follow your system manufacturer's recommended procedure for updating the CPU/firmware (typically via BIOS update or BMC firmware update)
  3. Verify the firmware version has been successfully applied after the update process completes
  4. Reboot the system to ensure the new firmware is active
Caveat Firmware updates carry inherent risk; ensure backups and a stable power supply before applying

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Epyc 7763 Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA8.0 h
44.0 hours of engineering $7,720
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-26339 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-26339 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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