CVE-2021-46778
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 · uneditedExecution unit scheduler contention may lead to a side channel vulnerability found on AMD CPU microarchitectures codenamed “Zen 1”, “Zen 2” and “Zen 3” that use simultaneous multithreading (SMT). By measuring the contention level on scheduler queues an attacker may potentially leak sensitive information.
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 confidenceExecution unit scheduler contention side channel in AMD Zen 1/2/3 CPUs with SMT enabled. By measuring contention levels on scheduler queues, an attacker can potentially leak sensitive information through a timing-based side channel attack.
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 dataall versionsall versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS 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
- High
- Privileges
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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 checksWork through these to decide whether this CVE applies to you.
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Identify your AMD CPU modelRun `lscpu | grep 'Model name'` or `cat /proc/cpuinfo | grep 'model name' | head -1` to see the exact CPU modelAffected if The CPU model matches one of the following: Amd Athlon 3050ge, 3150g, 3150ge, Amd Epyc 7001, 7002, 7003, 7232p, or 7251
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Verify SMT is enabledCheck the SMT status by running `cat /sys/devices/system/cpu/smt/active` or `lscpu | grep -i 'thread'` - a result of '1' or presence of multiple threads per core indicates SMT is activeAffected if SMT is currently enabled (value shows 1 or multiple threads per physical core)
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Confirm CPU architecture is Zen 1/2/3If your CPU model is not in the explicit list above, verify the microarchitecture by checking `/sys/devices/cpu/caps/` or AMD's processor specification database; Zen 1 (Ryzen 1000/2000 series, Epyc 7001), Zen 2 (Ryzen 3000/4000 series, Epyc 7002), and Zen 3 (Ryzen 5000 series, Epyc 7003) are affectedAffected if CPU uses Zen 1, Zen 2, or Zen 3 microarchitecture and SMT is enabled
Your system is affected if you run an AMD Zen 1/2/3-based processor (specifically Athlon 3050ge/3150g/3150ge or Epyc 7001/7002/7003/7232p/7251) with SMT currently enabled in the BIOS/UEFI or operating system.
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 dataDisable SMT (Simultultaneous Multithreading) in BIOS/UEFI settings on affected systems, or apply AMD microcode/firmware updates if available; this may carry performance implications.
- Consultation8.0 h
- Implementation4.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-46778 — 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-2021-46778 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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- Version or environment caveats, and links to real fixes
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