CVE-2020-1662

CVE-2020-1662 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-20.

Key facts

Description

On Juniper Networks Junos OS and Junos OS Evolved devices, BGP session flapping can lead to a routing process daemon (RPD) crash and restart, limiting the attack surface to configured BGP peers. This issue only affects devices with BGP damping in combination with accepted-prefix-limit configuration. When the issue occurs the following messages will appear in the /var/log/messages: rpd[6046]: %DAEMON-4-BGP_PREFIX_THRESH_EXCEEDED: XXXX (External AS x): Configured maximum accepted prefix-limit threshold(1800) exceeded for inet6-unicast nlri: 1984 (instance master) rpd[6046]: %DAEMON-3-BGP_CEASE_PREFIX_LIMIT_EXCEEDED: 2001:x:x:x::2 (External AS x): Shutting down peer due to exceeding configured maximum accepted prefix-limit(2000) for inet6-unicast nlri: 2001 (instance master) rpd[6046]: %DAEMON-4: bgp_rt_maxprefixes_check_common:9284: NOTIFICATION sent to 2001:x:x:x::2 (External AS x): code 6 (Cease) subcode 1 (Maximum Number of Prefixes Reached) AFI: 2 SAFI: 1 prefix limit 2000 kernel: %KERN-5: mastership_relinquish_on_process_exit: RPD crashed on master RE. Sending SIGUSR2 to chassisd (5612:chassisd) to trigger RE switchover This issue affects: Juniper Networks Junos OS: 17.2R3-S3; 17.3 version 17.3R3-S3 and later versions, prior to 17.3R3-S8; 17.4 version 17.4R2-S4, 17.4R3 and later versions, prior to 17.4R2-S10, 17.4R3-S2; 18.1 version 18.1R3-S6 and later versions, prior to 18.1R3-S10; 18.2 version 18.2R3 and later versions, prior to 18.2R3-S4; 18.2X75 version 18.2X75-D50, 18.2X75-D60 and later versions, prior to 18.2X75-D53, 18.2X75-D65; 18.3 version 18.3R2 and later versions, prior to 18.3R2-S4, 18.3R3-S2; 18.4 version 18.4R2 and later versions, prior to 18.4R2-S5, 18.4R3-S2; 19.1 version 19.1R1 and later versions, prior to 19.1R2-S2, 19.1R3-S1; 19.2 version 19.2R1 and later versions, prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2; 20.1 versions prior to 20.1R1-S2, 20.1R2. Juniper Networks Junos OS Evolved prior to 20.1R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 17.2R3-S3.

Frequently asked questions

What is CVE-2020-1662?
On Juniper Networks Junos OS and Junos OS Evolved devices, BGP session flapping can lead to a routing process daemon (RPD) crash and restart, limiting the attack surface to configured BGP peers. This issue only affects devices with BGP damping in combination with accepted-prefix-limit configuration. When the issue occurs the following messages will appear in the /var/log/messages: rpd[6046]: %DAEMON-4-BGP_PREFIX_THRESH_EXCEEDED: XXXX (External AS x): Configured maximum accepted prefix-limit threshold(1800) exceeded for inet6-unicast nlri: 1984 (instance master) rpd[6046]: %DAEMON-3-BGP_CEASE_PREFIX_LIMIT_EXCEEDED: 2001:x:x:x::2 (External AS x): Shutting down peer due to exceeding configured maximum accepted prefix-limit(2000) for inet6-unicast nlri: 2001 (instance master) rpd[6046]: %DAEMON-4: bgp_rt_maxprefixes_check_common:9284: NOTIFICATION sent to 2001:x:x:x::2 (External AS x): code 6 (Cease) subcode 1 (Maximum Number of Prefixes Reached) AFI: 2 SAFI: 1 prefix limit 2000 kernel: %KERN-5: mastership_relinquish_on_process_exit: RPD crashed on master RE. Sending SIGUSR2 to chassisd (5612:chassisd) to trigger RE switchover This issue affects: Juniper Networks Junos OS: 17.2R3-S3; 17.3 version 17.3R3-S3 and later versions, prior to 17.3R3-S8; 17.4 version 17.4R2-S4, 17.4R3 and later versions, prior to 17.4R2-S10, 17.4R3-S2; 18.1 version 18.1R3-S6 and later versions, prior to 18.1R3-S10; 18.2 version 18.2R3 and later versions, prior to 18.2R3-S4; 18.2X75 version 18.2X75-D50, 18.2X75-D60 and later versions, prior to 18.2X75-D53, 18.2X75-D65; 18.3 version 18.3R2 and later versions, prior to 18.3R2-S4, 18.3R3-S2; 18.4 version 18.4R2 and later versions, prior to 18.4R2-S5, 18.4R3-S2; 19.1 version 19.1R1 and later versions, prior to 19.1R2-S2, 19.1R3-S1; 19.2 version 19.2R1 and later versions, prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2; 20.1 versions prior to 20.1R1-S2, 20.1R2. Juniper Networks Junos OS Evolved prior to 20.1R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 17.2R3-S3.
How severe is CVE-2020-1662?
CVE-2020-1662 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-2020-1662 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-1662?
CVE-2020-1662 primarily affects Juniper Junos. In total, 59 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-1662?
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-2020-1662 published?
CVE-2020-1662 was published on 2020-10-16 and last updated on 2026-06-17.

References

Affected products (59)

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