title: Junos OS and Junos OS Evolved: BGP session flaps on NSR-enabled devices can cause rpd crash
description:
An Improper Handling of Exceptional Conditions vulnerability in BGP session processing of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated network-based attacker, using specific timing outside the attacker's control, to flap BGP sessions and cause the routing protocol daemon (rpd) process to crash and restart, leading to a Denial of Service (DoS) condition. Continued BGP session flapping will create a sustained Denial of Service (DoS) condition.
This issue only affects routers configured with non-stop routing (NSR) enabled. Graceful Restart (GR) helper mode, enabled by default, is also required for this issue to be exploitable.
Note: NSR is not supported on the SRX Series and is therefore not affected by this vulnerability.
When the BGP session flaps on the NSR-enabled router, the device enters GR-helper/LLGR-helper mode due to the peer having negotiated GR/LLGR-restarter capability and the backup BGP requests for replication of the GR/LLGR-helper session, master BGP schedules, and initiates replication of GR/LLGR stale routes to the backup BGP. In this state, if the BGP session with the BGP peer comes up again, unsolicited replication is initiated for the peer without cleaning up the ongoing GR/LLGR-helper mode replication. This parallel two instances of replication for the same peer leads to the assert if the BGP session flaps again.
This issue affects:
Juniper Networks Junos OS
*  All versions earlier than 20.4R3-S9;
*  21.2 versions earlier than 21.2R3-S7;
*  21.3 versions earlier than 21.3R3-S5;
*  21.4 versions earlier than 21.4R3-S5;
*  22.1 versions earlier than 22.1R3-S4;
*  22.2 versions earlier than 22.2R3-S3;
*  22.3 versions earlier than 22.3R3-S1;
*  22.4 versions earlier than 22.4R2-S2, 22.4R3;
*  23.2 versions earlier than 23.2R1-S1, 23.2R2.
Juniper Networks Junos OS Evolved
*  All versions earlier than 21.3R3-S5-EVO;
*  21.4 versions earlier than 21.4R3-S5-EVO;
*  22.1 versions earlier than 22.1R3-S4-EVO;
*  22.2 versions earlier than 22.2R3-S3-EVO;
*  22.3 versions earlier than 22.3R3-S1-EVO;
*  22.4 versions earlier than 22.4R2-S2-EVO, 22.4R3-EVO;
*  23.2 versions earlier than 23.2R1-S1-EVO, 23.2R2-EVO.
problem types: CWE-755 Improper Handling of Exceptional Conditions
affected:
{
defaultStatus: unaffected
platforms: [MX Series, PTX Series, ACX Series, EX Series, QFX Series]
product: Junos OS
vendor: Juniper Networks
versions:
lessThan: 20.4R3-S9, status: affected, version: 0, versionType: semver
lessThan: 21.2R3-S7, status: affected, version: 21.2, versionType: semver
lessThan: 21.3R3-S5, status: affected, version: 21.3, versionType: semver
lessThan: 21.4R3-S5, status: affected, version: 21.4, versionType: semver
lessThan: 22.1R3-S4, status: affected, version: 22.1, versionType: semver
lessThan: 22.2R3-S3, status: affected, version: 22.2, versionType: semver
lessThan: 22.3R3-S1, status: affected, version: 22.3, versionType: semver
lessThan: 22.4R2-S2, 22.4R3, status: affected, version: 22.4, versionType: semver
lessThan: 23.2R1-S1, 23.2R2, status: affected, version: 23.2, versionType: semver
}
{
defaultStatus: unaffected
platforms: [PTX Series, ACX Series, QFX Series]
product: Junos OS Evolved
vendor: Juniper Networks
versions:
lessThan: 21.3R3-S5-EVO, status: affected, version: 0, versionType: semver
lessThan: 21.4R3-S5-EVO, status: affected, version: 21.4, versionType: semver
lessThan: 22.1R3-S4-EVO, status: affected, version: 22.1, versionType: semver
lessThan: 22.2R3-S3-EVO, status: affected, version: 22.2, versionType: semver
lessThan: 22.3R3-S1-EVO, status: affected, version: 22.3, versionType: semver
lessThan: 22.4R2-S2-EVO, 22.4R3-EVO, status: affected, version: 22.4, versionType: semver
lessThan: 23.2R1-S1-EVO, 23.2R2-EVO, status: affected, version: 23.2, versionType: semver
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 5.9
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.1
]
format: CVSS
scenarios: GENERAL
exploits: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
solutions: The following software releases have been updated to resolve this specific issue:
Junos OS: 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S1, 22.4R2-S2, 22.4R3, 23.1R2, 23.2R1-S1, 23.2R2, 23.3R1, and all subsequent releases.
Junos OS Evolved: 21.3R3-S5-EVO, 21.4R3-S5-EVO, 22.1R3-S4-EVO, 22.2R3-S3-EVO, 22.3R3-S1-EVO, 22.4R2-S2-EVO, 22.4R3-EVO, 23.1R2-EVO, 23.2R1-S1-EVO, 23.2R2-EVO, 23.3R1-EVO, and all subsequent releases.
workarounds: Graceful Restart (GR) helper mode and Long-Lived Graceful Restart (LLGR) helper mode can be disabled to prevent this issue.
[edit protocols bgp graceful-restart]
disable;
[edit protocols bgp graceful-restart long-lived receiver]
disable;
