CVE-2024-21585

Junos OS and Junos OS Evolved: BGP session flaps on NSR-enabled devices can cause rpd crash

MEDIUM

5.9

CVSS Score

Published: January 12, 2024 at 12:50 AM UTC

Updated: June 17, 2026 at 07:09 AM UTC

3 products affected across 2 vendorsJunosJunos OS EvolvedJunos OS Evolved

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Severity

MEDIUM5.9

Exploit prediction

EPSS 0.6%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

v < 20.4R3-S921.2 ≤ v < 21.2R3-S721.3 ≤ v < 21.3R3-S521.4 ≤ v < 21.4R3-S522.1 ≤ v < 22.1R3-S422.2 ≤ v < 22.2R3-S322.3 ≤ v < 22.3R3-S122.4 ≤ v < 22.4R2-S2, 22.4R323.2 ≤ v < 23.2R1-S1, 23.2R220.4 20.4 r1 20.4 r1-s1 20.4 r2 20.4 r2-s1 20.4 r2-s2 20.4 r3 20.4 r3-s1 20.4 r3-s2 20.4 r3-s3 20.4 r3-s4 20.4 r3-s5 20.4 r3-s6 20.4 r3-s7 20.4 r3-s8 21.2 21.2 r1 21.2 r1-s1 21.2 r1-s2 21.2 r2 21.2 r2-s1 21.2 r2-s2 21.2 r3 21.2 r3-s1 21.2 r3-s2 21.2 r3-s3 21.2 r3-s4 21.2 r3-s5 21.2 r3-s6 21.3 21.3 r1 21.3 r1-s1 21.3 r1-s2 21.3 r2 21.3 r2-s1 21.3 r2-s2 21.3 r3 21.3 r3-s1 21.3 r3-s2 21.3 r3-s3 21.3 r3-s4 21.4 21.4 r1 21.4 r1-s1 21.4 r1-s2 21.4 r2 21.4 r2-s1 21.4 r2-s2 21.4 r3 21.4 r3-s1 21.4 r3-s2 21.4 r3-s3 21.4 r3-s4 22.1 22.1 r1 22.1 r1-s1 22.1 r1-s2 22.1 r2 22.1 r2-s1 22.1 r2-s2 22.1 r3 22.1 r3-s1 22.1 r3-s2 22.1 r3-s3 22.2 22.2 r1 22.2 r1-s1 22.2 r1-s2 22.2 r2 22.2 r2-s1 22.2 r2-s2 22.2 r3 22.2 r3-s1 22.2 r3-s2 22.3 22.3 r1 22.3 r1-s1 22.3 r1-s2 22.3 r2 22.3 r2-s1 22.3 r2-s2 22.3 r3 22.4 22.4 r1 22.4 r1-s1 22.4 r1-s2 22.4 r2 22.4 r2-s1 23.2 23.2 r1

Affected range stops below 20.4R3-S9, so it looks safe — our inference, not a vendor statement

Affected range stops below 21.2R3-S7, so it looks safe — our inference, not a vendor statement

Affected range stops below 21.3R3-S5, so it looks safe — our inference, not a vendor statement

Affected range stops below 21.4R3-S5, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.1R3-S4, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.2R3-S3, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.3R3-S1, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.4R2-S2, 22.4R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.2R1-S1, 23.2R2, so it looks safe — our inference, not a vendor statement

Junos OS Evolved · Juniper Networks

60%

v < 21.3R3-S5-EVO21.4 ≤ v < 21.4R3-S5-EVO22.1 ≤ v < 22.1R3-S4-EVO22.2 ≤ v < 22.2R3-S3-EVO22.3 ≤ v < 22.3R3-S1-EVO22.4 ≤ v < 22.4R2-S2-EVO, 22.4R3-EVO23.2 ≤ v < 23.2R1-S1-EVO, 23.2R2-EVO21.4 22.1 22.2 22.3 22.4 23.2

Affected range stops below 21.3R3-S5-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 21.4R3-S5-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.1R3-S4-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.2R3-S3-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.3R3-S1-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.4R2-S2-EVO, 22.4R3-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.2R1-S1-EVO, 23.2R2-EVO, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (3)

Vendor Advisory

Source: [email protected]

https://supportportal.juniper.net/JSA75723

ProductVendor Advisory

Source: [email protected]

https://supportportal.juniper.net/s/article/MX-GR-and-LLGR-capability-and-compatibility-changes-after-15-1-release

Technical DescriptionThird Party Advisory

Source: [email protected]

https://www.first.org/cvss/calculator/4.0#CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.9MEDIUMjuniper

Attack Vector: NETWORK
Complexity: HIGH
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-755

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