Juniper Junos OS/Junos OS Evolved prior 23.2R1/23.2R2/23.4R1-S2/23.4R2/24.1R2 Routing Protocol Daemon memory leak

Summaryinfo

A vulnerability classified as problematic has been found in Juniper Junos OS and Junos OS Evolved. This affects an unknown function of the component Routing Protocol Daemon. The manipulation leads to memory leak. This vulnerability is traded as CVE-2026-21909. Access to the local network is required for this attack to succeed. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Juniper Junos OS and Junos OS Evolved. It has been rated as critical. This issue affects some unknown processing of the component Routing Protocol Daemon. The manipulation with an unknown input leads to a memory leak vulnerability. Using CWE to declare the problem leads to CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. Impacted is availability. The summary by CVE is:

A Missing Release of Memory after Effective Lifetime vulnerability in the routing protocol daemon (rpd) Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated attacker controlling an adjacent IS-IS neighbor to send a specific update packet causing a memory leak. Continued receipt and processing of these packets will exhaust all available memory, crashing rpd and creating a Denial of Service (DoS) condition. Memory usage can be monitored through the use of the 'show task memory detail' command. For example: user@junos> show task memory detail | match ted-infra   TED-INFRA-COOKIE           25   1072     28   1184     229 user@junos> show task memory detail | match ted-infra   TED-INFRA-COOKIE           31   1360     34   1472     307 This issue affects: Junos OS:  * from 23.2 before 23.2R2,  * from 23.4 before 23.4R1-S2, 23.4R2,  * from 24.1 before 24.1R2;  Junos OS Evolved:  * from 23.2 before 23.2R2-EVO,  * from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO,  * from 24.1 before 24.1R2-EVO. This issue does not affect Junos OS versions before 23.2R1 or Junos OS Evolved versions before 23.2R1-EVO.

It is possible to read the advisory at supportportal.juniper.net. The identification of this vulnerability is CVE-2026-21909 since 01/05/2026. The exploitation is known to be easy. Access to the local network is required for this attack to succeed. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 23.2R1, 23.2R2, 23.4R1-S2, 23.4R2 or 24.1R2 eliminates this vulnerability.

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Productinfo

Type

• Router Operating System

Vendor

• Juniper

Name

• Junos OS
• Junos OS Evolved

License

• commercial

Website

• Vendor: https://www.juniper.net/

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