Security readout for executives and security teams
Plain-English summary
This Junos OS flaw can let an unauthenticated network attacker crash and restart an affected Juniper device by sending specific packet sequences addressed to the device. The business risk is service outage, not data theft, but repeated traffic can sustain denial of service on exposed infrastructure.
Executive priority
Treat this as a high-priority availability risk for Juniper infrastructure. It does not indicate confidentiality compromise, but a repeatable device crash can disrupt network services. Patch exposed and critical devices first, then complete fleet-wide remediation.
Technical view
CVE-2021-0283 is a CWE-120 buffer overflow in the Junos OS TCP/IP stack. It is remotely reachable, low complexity, requires no privileges or user interaction, and affects availability only. The issue is triggered by packets destined to the device; transit traffic is not reported to trigger it.
Likely exposure
Organizations running affected Junos OS releases from the listed 12.3 through 21.2 trains may be exposed. Risk is highest where untrusted networks can send traffic addressed directly to the Junos device, including reachable routing, infrastructure, or management-facing interfaces.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. Juniper states repeated packet sequences can sustain denial of service. A cited indicator is the log message: "SYSTEM_ABNORMAL_SHUTDOWN: System abnormally shut down".
Researcher notes
Validation should focus on version exposure, device-destined reachability, abnormal shutdown logs, and vmcore evidence. Do not assume transit traffic is exploitable based on the provided sources. The bundle provides vendor-confirmed affected ranges but no evidence of active exploitation.
Mitigation direction
- Identify all Junos OS devices and compare versions against Juniper's affected and fixed release ranges.
- Upgrade affected devices to a Juniper-fixed release listed in the advisory.
- Restrict untrusted traffic destined directly to Junos devices where operationally feasible.
- Prioritize internet-facing or broadly reachable infrastructure devices before lower-exposure internal systems.
- Monitor Juniper guidance for platform-specific workarounds or updated fixed-release recommendations.
Validation and detection
- Inventory Junos OS versions across routers, switches, and security devices.
- Check logs for SYSTEM_ABNORMAL_SHUTDOWN messages and unexpected vmcore generation.
- Confirm whether untrusted hosts can reach traffic paths addressed to each device.
- Review recent availability incidents for unexplained kernel crashes or restarts.
- After upgrades, verify devices run fixed Junos OS releases from Juniper's advisory.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-120: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-0283 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11200CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.