CVE-2021-0283
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 buffer overflow vulnerability in the TCP/IP stack of Juniper Networks Junos OS allows an attacker to send specific sequences of packets to the device thereby causing a Denial of Service (DoS). By repeatedly sending these sequences of packets to the device, an attacker can sustain the Denial of Service (DoS) condition. The device will abnormally shut down as a result of these sent packets. A potential indicator of compromise will be the following message in the log files: "eventd[13955]: SYSTEM_ABNORMAL_SHUTDOWN: System abnormally shut down" These issue are only triggered by traffic destined to the device. Transit traffic will not trigger these issues. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S19; 15.1 versions prior to 15.1R7-S10; 16.1 version 16.1R1 and later versions; 16.2 version 16.2R1 and later versions; 17.1 version 17.1R1 and later versions; 17.2 version 17.2R1 and later versions; 17.3 versions prior to 17.3R3-S12; 17.4 version 17.4R1 and later versions; 18.1 versions prior to 18.1R3-S13; 18.2 version 18.2R1 and later versions; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S7, 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2-S1, 20.4R3; 21.1 versions prior to 21.1R1-S1, 21.1R2; 21.2 versions prior to 21.2R1-S1, 21.2R2.
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 confidenceA buffer overflow vulnerability exists in the TCP/IP stack of Juniper Networks Junos OS. An attacker can send specific sequences of packets to the device, causing a Denial of Service where the device abnormally shuts down. The attack can be sustained repeatedly. This only affects traffic destined to the device, not transit traffic. Indicator of compromise: 'eventd[13955]: SYSTEM_ABNORMAL_SHUTDOWN: System abnormally shut down' in logs.
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= 12.3= 15.1= 16.1= 16.2= 17.1= 17.2= 17.3= 18.1= 18.2= 18.3= 18.4= 19.1CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify the Junos OS versionExecute 'show version' or 'show version detail' on the device CLI to retrieve the installed Junos OS versionAffected if The displayed version matches exactly 12.3, 15.1, 16.1, 16.2, 17.1, 17.2, 17.3, 18.1, 18.2, 18.3, 18.4, or 19.1
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Check for crash indicator in logsSearch system logs (using 'show log messages' or 'show syslog messages') for the string 'SYSTEM_ABNORMAL_SHUTDOWN' or 'eventd' combined with 'SYSTEM_ABNORMAL_SHUTDOWN'Affected if Log entries contain the pattern 'eventd[...]: SYSTEM_ABNORMAL_SHUTDOWN: System abnormally shut down' indicating the device has already been crashed by this vulnerability
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Assess management interface exposureReview firewall filter configurations and interface policies to determine if the device's management interfaces (HTTP, HTTPS, SSH, Telnet) are reachable from untrusted network sourcesAffected if Management interfaces are exposed to untrusted/internet-facing networks, since the flaw only affects traffic destined to the device (not transit traffic)
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Verify TCP/IP processing is enabledConfirm the device is actively processing TCP/IP traffic on its interfaces (check 'show interfaces terse' and confirm routing/TCP services are running)Affected if The device has active TCP/IP stack processing enabled, which is required for the malicious packets to trigger the buffer overflow
You are affected if your Junos OS version exactly matches one of the listed affected versions AND management interfaces are reachable from untrusted sources, especially if logs already show SYSTEM_ABNORMAL_SHUTDOWN events.
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 dataApply the vendor-supplied Junos OS patches/updates for the affected versions. Consider implementing firewall filters to limit exposure of management interfaces to untrusted sources until patching can be completed.
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- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-0283 — 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-2021-0283 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
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- Version or environment caveats, and links to real fixes
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