How severe is CVE-2020-1686?

CVE-2020-1686 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2020-1686 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-1686?

CVE-2020-1686 primarily affects Juniper Junos. In total, 34 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-1686?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-1686 published?

CVE-2020-1686 was published on 2020-10-16 and last updated on 2026-06-17.

CVE-2020-1686

CVE-2020-1686 is a high-severity vulnerability in Juniper Junos with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-415.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.8
EPSS exploit prediction: 1% (69th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-415
Affected product: Juniper Junos
Published: 2020-10-16
Last modified: 2026-06-17

Description

On Juniper Networks Junos OS devices, receipt of a malformed IPv6 packet may cause the system to crash and restart (vmcore). This issue can be trigged by a malformed IPv6 packet destined to the Routing Engine. An attacker can repeatedly send the offending packet resulting in an extended Denial of Service condition. Only IPv6 packets can trigger this issue. IPv4 packets cannot trigger this issue. This issue affects Juniper Networks Junos OS 18.4 versions prior to 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2. This issue does not affect Juniper Networks Junos OS prior to 18.4R1.

Frequently asked questions

What is CVE-2020-1686?: On Juniper Networks Junos OS devices, receipt of a malformed IPv6 packet may cause the system to crash and restart (vmcore). This issue can be trigged by a malformed IPv6 packet destined to the Routing Engine. An attacker can repeatedly send the offending packet resulting in an extended Denial of Service condition. Only IPv6 packets can trigger this issue. IPv4 packets cannot trigger this issue. This issue affects Juniper Networks Junos OS 18.4 versions prior to 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2. This issue does not affect Juniper Networks Junos OS prior to 18.4R1.
How severe is CVE-2020-1686?: CVE-2020-1686 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2020-1686 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-1686?: CVE-2020-1686 primarily affects Juniper Junos. In total, 34 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-1686?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-1686 published?: CVE-2020-1686 was published on 2020-10-16 and last updated on 2026-06-17.

References

https://kb.juniper.net/JSA11083

Affected products (34)

cpe:2.3:o:juniper:junos:18.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r1-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r1-s6:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r2-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:18.4:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:r1-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:r1-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.1:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.2:r1-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.2:r1-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.3:r2-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:19.4:r1-s2:*:*:*:*:*:*

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