Junos OS (SRX firewalls)
CVE-2024-21585: BGP session flaps on NSR-enabled devices can cause rpd crash
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.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 0 | 20.4R3-S9 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 21.2 | 21.2R3-S7 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 21.3 | 21.3R3-S5 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 21.4 | 21.4R3-S5 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 22.1 | 22.1R3-S4 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 22.2 | 22.2R3-S3 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 22.3 | 22.3R3-S1 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 22.4 | 22.4R2-S2, 22.4R3 or later |
| Junos OS (MX Series, PTX Series, ACX Series, EX Series, QFX Series) 23.2 | 23.2R1-S1, 23.2R2 or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 0 | 21.3R3-S5-EVO or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 21.4 | 21.4R3-S5-EVO or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 22.1 | 22.1R3-S4-EVO or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 22.2 | 22.2R3-S3-EVO or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 22.3 | 22.3R3-S1-EVO or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 22.4 | 22.4R2-S2-EVO, 22.4R3-EVO or later |
| Junos OS Evolved (PTX Series, ACX Series, QFX Series) 23.2 | 23.2R1-S1-EVO, 23.2R2-EVO or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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.
Am I affected?
Non-stop routing (NSR) is enabled using the following configuration:
[edit chassis redundancy] graceful-switchover;
[edit routing-options] nonstop-routing;
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;
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.