CVE-2021-34987
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 · uneditedThis vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop 16.5.1 (49187). An attacker must first obtain the ability to execute high-privileged code on the target guest system in order to exploit this vulnerability. The specific flaw exists within the HDAudio virtual device. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length buffer. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the hypervisor. Was ZDI-CAN-14969.
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 · high confidenceBuffer overflow vulnerability in Parallels Desktop's virtual HDAudio device allows a local attacker with high-privileged code execution on the guest VM to escape containment and execute arbitrary code in the hypervisor context. The flaw stems from insufficient validation of user-supplied data length before copying into a fixed-size buffer.
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= 16.5.1CVSS 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
- High
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Verify Parallels Desktop installationCheck if Parallels Desktop is installed by looking for /Applications/Parallels Desktop.app or running 'ls /Applications | grep -i parallels'Affected if Parallels Desktop is not installed on the system
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Determine installed Parallels Desktop versionOpen Parallels Desktop and go to Menu > About Parallels Desktop, or run 'defaults read /Applications/Parallels\ Desktop.app/Contents/Info.plist CFBundleShortVersionString'Affected if Version is exactly 16.5.1
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Confirm HDAudio virtual device is activeCheck VM configuration: open Parallels Desktop > select VM > Hardware > Sound, or examine VM's .pvs config file for HDAudio device presenceAffected if HDAudio virtual sound device is enabled for any guest VM
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Identify running guest VMsRun 'prlctl list -a' to list all VMs, or check Activity Monitor for parallels processesAffected if Any guest VMs are running with the vulnerable configuration
System is affected only if Parallels Desktop version 16.5.1 is installed AND HDAudio virtual device is enabled for any guest VM.
Generated from the published advisory. Verify against your own configuration.
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 dataUpdate Parallels Desktop to the vendor-patched version. This is a critical VM escape vulnerability requiring immediate remediation if exposed to untrusted guest workloads.
- Consultation2.0 h
- Implementation1.0 h
- Testing4.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-34987 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-34987 in production — separate from our analysis above.
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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- 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
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