VDB
CVE-2026-21921
CVE-2026-21921
PUBLISHED
CVSS 6.5 MEDIUM
A Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service (DoS). When telemetry collectors are frequently subscribing and unsubscribing to sensors continuously over a long period of time, telemetry-capable processes like chassisd, rpd or mib2d will crash and restart, which - depending on the process - can cause a complete outage until the system has recovered. This issue affects: Junos OS: * all versions before 22.4R3-S8, * 23.2 versions before 23.2R2-S5, * 23.4 versions before 23.4R2; Junos OS Evolved: * all versions before 22.4R3-S8-EVO, * 23.2 versions before 23.2R2-S5-EVO, * 23.4 versions before 23.4R2-EVO.
EPSS 0.02% · 6.2th percentile
Risk Scores
CVSS v3.1
6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS Score
0.02%
6.2th percentile
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Juniper Networks | Junos OS Evolved | 0, 23.2, 23.4 |
| juniper | junos_os_evolved | 23.2, 0, 22.4 |
| Juniper Networks | Junos OS | 23.4, 0, 23.2 |
| juniper | junos | 0, 22.4, 22.4 |
Timeline
- Jan 15, 2026 CVE Published
- Jan 15, 2026 CVE Updated
- Jan 15, 2026 PoC Published
- Jan 16, 2026 EPSS Score
- Jan 19, 2026 EPSS Score
- Jan 22, 2026 EPSS Score
- Jan 25, 2026 EPSS Score
- Jan 27, 2026 EPSS Score
- Jan 30, 2026 EPSS Score
- Feb 2, 2026 EPSS Score
- Feb 5, 2026 EPSS Score
- Feb 8, 2026 EPSS Score
References
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-and-Junos-OS-Evolved-Optional-transitive-BGP-attribute-is-modified-before-propagation-to-peers-causing-sessions-to-flap-CVE-2025-60011 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-and-Junos-OS-Evolved-When-telemetry-collectors-are-frequently-subscribing-and-unsubscribing-to-sensors-chassisd-or-rpd-will-crash-CVE-2026-21921 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-EX4000-A-high-volume-of-traffic-destinated-to-the-device-leads-to-a-crash-and-restart-CVE-2026-21913 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-Receipt-of-a-specifically-malformed-ICMP-packet-causes-an-FPC-restart-CVE-2026-0203 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-Space-TLS-SSL-server-supports-use-of-static-key-ciphers-ssl-static-key-ciphers-CVE-2026-21907 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-and-Junos-OS-Evolved-BGP-update-with-a-set-of-specific-attributes-causes-rpd-crash-CVE-2025-60003 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-Evolved-Flapping-management-interface-causes-MAC-learning-on-label-switched-interfaces-to-stop-CVE-2026-21911 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-and-Junos-OS-Evolved-Receipt-of-specific-IS-IS-update-packet-causes-memory-leak-leading-to-RPD-crash-CVE-2026-21909 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-Subscribing-to-telemetry-sensors-at-scale-causes-all-FPCs-to-crash-CVE-2026-21903 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-SRX-Series-Specifically-malformed-SSL-packet-causes-FPC-crash-CVE-2026-21917 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-Space-Multiple-vulnerabilities-resolved-in-24-1R5-release advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-SRX-Series-A-specifically-malformed-GTP-message-will-cause-an-FPC-crash-CVE-2026-21914 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-and-Junos-OS-Evolved-Use-after-free-vulnerability-In-802-1X-authentication-daemon-can-cause-crash-of-the-dot1xd-process-CVE-2026-21908 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-A-specifically-crafted-show-chassis-command-causes-chassisd-to-crash-CVE-2025-60007 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-and-Junos-OS-Evolved-Unix-socket-used-to-control-the-jdhcpd-process-is-world-writable-CVE-2025-59961 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Policy-Enforcer-Multiple-vulnerabilities-in-Python-resolved-in-24-1R3-release advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-EX4k-Series-QFX5k-Series-In-an-EVPN-VXLAN-configuration-link-flaps-cause-Inter-VNI-traffic-drop-CVE-2026-21910 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-SRX-Series-With-GRE-performance-acceleration-enabled-receipt-of-a-specific-ICMP-packet-causes-the-PFE-to-crash-CVE-2026-21906 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-SRX-and-MX-Series-When-TCP-packets-occur-in-a-specific-sequence-flowd-crashes-CVE-2026-21918 advisory
- https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-SRX-Series-If-a-specific-request-is-processed-by-the-DNS-subsystem-flowd-will-crash-CVE-2026-21920 advisory
…and 6 more