CVE-2020-1662

Junos OS and Junos OS Evolved: RPD crash due to BGP session flapping.

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.

Remediation

Solution:

  • The following software releases have been updated to resolve this specific issue: Junos OS: 17.2R3-S4, 17.3R3-S8, 17.3R3-S9, 17.4R2-S10, 17.4R3-S2, 18.1R3-S10, 18.2R3-S4, 18.2X75-D53, 18.2X75-D65, 18.3R2-S4, 18.3R3-S2, 18.4R2-S5, 18.4R3-S2, 19.1R2-S2, 19.1R3-S1, 19.2R1-S5, 19.2R2, 19.3R2-S3, 19.3R3, 19.4R1-S3, 19.4R2, 20.1R1-S2, 20.1R2, 20.2R1, and all subsequent releases. Junos OS Evolved: 20.1R2-EVO, and all subsequent releases.

Workaround:

  • There are multiple workarounds that can be applied to prevent this issue: 1. Disable BGP router flap damping. 2. Replace "accepted-prefix-limit" with "prefix-limit" in the BGP configuration, for example: [edit protocols bgp group ${GRP} neighbor ${NEI} family ${AFI} unicast] + prefix-limit { - accepted-prefix-limit { 3. Make sure that the BGP session idle-timeout is longer than damping max-suppress time. In other words, by the time a peer is eligible to establish BGP session again, no previously advertised prefixes remain suppressed. The BGP session idle time out is configured under: [protocols bgp damping ... teardown idle-timeout ] The BGP damping max-suppress time configured under: [protocol bgp damping... max-suppress ] The needs to be higher than

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.61%
Vendor Advisory juniper.net
Affected: Juniper Networks Junos OS
Affected: Juniper Networks Junos OS Evolved
Published at:
Updated at:

References

Link Tags
https://kb.juniper.net/JSA11059 vendor advisory

Frequently Asked Questions

What is the severity of CVE-2020-1662?
CVE-2020-1662 has been scored as a high severity vulnerability.
How to fix CVE-2020-1662?
To fix CVE-2020-1662: The following software releases have been updated to resolve this specific issue: Junos OS: 17.2R3-S4, 17.3R3-S8, 17.3R3-S9, 17.4R2-S10, 17.4R3-S2, 18.1R3-S10, 18.2R3-S4, 18.2X75-D53, 18.2X75-D65, 18.3R2-S4, 18.3R3-S2, 18.4R2-S5, 18.4R3-S2, 19.1R2-S2, 19.1R3-S1, 19.2R1-S5, 19.2R2, 19.3R2-S3, 19.3R3, 19.4R1-S3, 19.4R2, 20.1R1-S2, 20.1R2, 20.2R1, and all subsequent releases. Junos OS Evolved: 20.1R2-EVO, and all subsequent releases.
Is CVE-2020-1662 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2020-1662 is being actively exploited. According to its EPSS score, there is a ~1% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2020-1662?
CVE-2020-1662 affects Juniper Networks Junos OS, Juniper Networks Junos OS Evolved.
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