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2020-10 Security Bulletin: Junos OS: Kernel crash (vmcore) upon receipt of a malformed IPv6 packet. (CVE-2020-1686)



Article ID: JSA11083 SECURITY_ADVISORIES Last Updated: 28 Oct 2020Version: 3.0
Product Affected:
This issue affects Junos OS 18.4, 19.1, 19.2, 19.3, 19.4.

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.

The example of the configuration stanza affected by this issue is as follows:

[interfaces <interface_name> unit <unit_num> family inet6]

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2020-1686.


The following software releases have been updated to resolve this specific issue: Junos OS 18.4R2-S4, 18.4R3-S1, 19.1R2-S1, 19.1R3, 19.2R1-S5, 19.2R2, 19.3R2-S4, 19.3R3, 19.4R1-S3, 19.4R2, 19.4R2-S1, 20.1R1, and all subsequent releases.

This issue is being tracked as 1486948.


Standard security best common practices such as limiting packet toward the RE only from trusted networks/host using firewall filter in combination with source address anti-spoofing should be applied to reduce the risk of exposure.

Software releases or updates are available for download at
Modification History:
2020-10-14: Initial Publication.
2020-10-28: Removing reference with regards to this issue can be caused by a transit packet that is sampled using sFlow/jFlow or processed by firewall filter with the syslog and/or log action.

CVSS Score:
7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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