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NVD / CVE Program· CNA juniper

CVE-2021-0226: Junos OS Evolved: The IPv6 BGP session will flap due to receipt of a specific IPv6 packet

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.87% (FIRST EPSS); higher than 59.2% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

On Juniper Networks Junos OS Evolved devices, receipt of a specific IPv6 packet may cause an established IPv6 BGP session to terminate, creating a Denial of Service (DoS) condition. Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue does not affect IPv4 BGP sessions. This issue affects IBGP or EBGP peer sessions with IPv6. This issue affects: Juniper Networks Junos OS Evolved: 19.4 versions prior to 19.4R2-S3-EVO; 20.1 versions prior to 20.1R2-S3-EVO; 20.2 versions prior to 20.2R2-S1-EVO; 20.3 versions prior to 20.3R2-EVO. This issue does not affect Juniper Networks Junos OS releases.

HighCVSS 7.5 · v3.1—No exploit No fix recorded
Published
Apr 22, 2021
Updated
Jun 16, 2026
EPSS
0.8% · 59th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

CNA vs NVD score

NVD
7.5
CNA · juniper
7.1
0.4 point gap

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-0226

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
juniperjunos os evolved

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • juniper junos os evolved20.1
  • juniper junos os evolved20.2
  • juniper junos os evolved20.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (juniper). Independent of NVD's CPE analysis and usually ahead of it.

  • Juniper Networks Junos OS Evolved

    • 19.4-EVO and later · before 19.4R2-S3-EVOaffected
    • 20.1-EVO and later · before 20.1R2-S3-EVOaffected
    • 20.2-EVO and later · before 20.2R2-S1-EVOaffected
    • 20.3-EVO and later · before 20.3R2-EVOaffected

Same product

juniper: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-21902Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root
    43Plan
  • CVE-2026-101990Junos OS and Junos OS Evolved: A BGP peer causes an rpd crash when flow-spec routes are re-advertised
    37Monitor
  • CVE-2026-101986Junos OS and Junos OS Evolved: J-Web permits pre-authentication CGI execution
    37Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-0209Jan 15, 2021 · Junos OS Evolved: Receipt of certain valid BGP update packets from BGP peers may cause RPD to core when using REGEX.
    26Monitor
  • ← EarlierCVE-2021-0225Apr 22, 2021 · Junos OS Evolved: Stateless IP firewall filter does not work as expected
    23Monitor
  • Later →CVE-2021-0239Apr 22, 2021 · Junos OS Evolved: Denial of Service due to receipt of specific genuine layer 2 frames.
    26Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-665 · Improper Initialization

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records