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XenOperating system

CVE-2021-28693

MEDIUM · 5.5 CVSS v3.1 Published 2021-06-30
Fix available
A fix is available. Upgrade to after 4.15.0 or later.
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
xen/arm: Boot modules are not scrubbed The bootloader will load boot modules (e.g. kernel, initramfs...) in a temporary area before they are copied by Xen to each domain memory. To ensure sensitive data is not leaked from the modules, Xen must "scrub" them before handing the page over to the allocator. Unfortunately, it was discovered that modules will not be scrubbed on Arm.

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

On Xen ARM systems, boot modules (kernel, initramfs) loaded by the bootloader into temporary memory are not scrubbed (cleared) before being returned to the memory allocator. This can lead to sensitive data from boot modules leaking to other domains when that memory is reallocated.

MitigationUpgrade Xen to the patched version that implements proper memory scrubbing for boot modules on ARM architecture.

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
XenOperating system
Affected:>= 4.12.0, <= 4.15.0= 4.15.0

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
High
Integrity
None
Availability
None

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

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. Confirm system architecture is ARM
    Run 'uname -m' or check /proc/cpuinfo. Look for 'aarch64' or 'arm' in the output. This vulnerability only affects ARM systems, not x86.
    Affected if Architecture is ARM/aarch64 and the system runs Xen as the hypervisor
  2. Check installed Xen version
    Run 'xl version' or 'xm version' to display the Xen hypervisor version. Alternatively, check '/usr/lib/xen/bin/xe-toolstack' --version or the Xen package version via the system package manager.
    Affected if Version is 4.12.0, 4.13.0, 4.14.0, or 4.15.0 (any version from 4.12.0 through 4.15.0)
  3. Verify boot modules are in use
    Check bootloader configuration (e.g., Xen config files in /etc/xen/ or examined via 'xl cfglist' or 'xm list -l'). Look for 'kernel' and 'initrd' or 'ramdisk' directives that specify boot modules.
    Affected if Boot modules (kernel, initramfs) are loaded - the vulnerability only triggers when boot modules exist in the configuration

A system is affected if it is running on ARM architecture with Xen version 4.12.0 through 4.15.0 and has boot modules (kernel/initramfs) configured for guest domains.

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.

From vendor data
Upgrade available Upgrade to a release after 4.15.0
Interim mitigation

Upgrade Xen to the patched version that implements proper memory scrubbing for boot modules on ARM architecture.

Fix this in Xen 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 the upgrade done

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

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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-2021-28693 in production — separate from our analysis above.

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