CVE-2021-0294
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 · uneditedA vulnerability in Juniper Networks Junos OS, which only affects the release 18.4R2-S5, where a function is inconsistently implemented on Juniper Networks Junos QFX5000 Series and EX4600 Series, and if "storm-control enhanced" is configured, can lead to the enhanced storm control filter group not be installed. It will cause storm control not to work hence allowing an attacker to cause high CPU usage or packet loss issues by sending a large amount of broadcast or unknown unicast packets arriving the device. This issue affects Juniper Networks QFX5100, QFX5110, QFX5120, QFX5200, QFX5210, EX4600, and EX4650, and QFX5100 with QFX 5e Series image installed. QFX5130 and QFX5220 are not affected from this issue. This issue affects Juniper Networks Junos OS 18.4R2-S5 on QFX5000 Series and EX4600 Series. No other product or platform is affected by this vulnerability.
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 confidenceIn Junos OS 18.4R2-S5 on QFX5000 and EX4600 series switches, a function is inconsistently implemented such that when 'storm-control enhanced' is configured, the enhanced storm control filter group fails to install. This leaves storm control non-functional, allowing attackers to flood the device with broadcast or unknown unicast traffic, causing high CPU usage or packet loss.
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= 18.4CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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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Confirm device is QFX5000 or EX4600 seriesRun 'show chassis hardware' or 'show version' to identify the exact model number of the switchAffected if Device model is not QFX5000 or EX4600 series - not affected by this specific CVE
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Check Junos OS versionRun 'show version' and verify the exact Junos version is 18.4R2-S5Affected if Version is not 18.4R2-S5 - not affected by this specific CVE (only that exact version is listed as affected)
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Verify storm-control enhanced configurationRun 'show configuration | match storm-control' and check for the 'storm-control enhanced' hierarchy under the relevant interface or physical port configurationAffected if The 'storm-control enhanced' configuration is NOT present - not affected (the flaw only manifests when this feature is configured)
Device is affected only if it is a QFX5000 or EX4600 series switch running Junos OS 18.4R2-S5 AND has 'storm-control enhanced' configured, as the vulnerability causes the storm control filter to fail to install under those specific conditions.
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 dataUpgrade from Junos OS 18.4R2-S5 to a fixed version (not specified in advisory). Alternatively, avoid using 'storm-control enhanced' configuration or implement alternative traffic filtering/segmentation at adjacent network points.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-0294 — 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-2021-0294 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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