Juniper Junos OS/Junos OS Evolved prior 24.2R2 BGP Update use after free

Summaryinfo

A vulnerability classified as critical was found in Juniper Junos OS and Junos OS Evolved. This affects an unknown function of the component BGP Update Handler. Such manipulation leads to use after free. This vulnerability is listed as CVE-2025-52946. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Juniper Junos OS and Junos OS Evolved and classified as critical. Affected by this issue is an unknown function of the component BGP Update Handler. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is availability. CVE summarizes:

A Use After Free vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Juniper Networks Junos OS Evolved allows an attacker sending a BGP update with a specifically malformed AS PATH to cause rpd to crash, resulting in a Denial of Service (DoS). Continuous receipt of the malformed AS PATH attribute will cause a sustained DoS condition. On all Junos OS and Junos OS Evolved platforms, the rpd process will crash and restart when a specifically malformed AS PATH is received within a BGP update and traceoptions are enabled. This issue only affects systems with BGP traceoptions enabled and requires a BGP session to be already established. Systems without BGP traceoptions enabled are not impacted by this issue. This issue affects:  Junos OS: * All versions before 21.2R3-S9,  * all versions of 21.4, * from 22.2 before 22.2R3-S6,  * from 22.4 before 22.4R3-S5,  * from 23.2 before 23.2R2-S3,  * from 23.4 before 23.4R2-S4,  * from 24.2 before 24.2R2;  Junos OS Evolved:  * All versions before 22.4R3-S5-EVO,  * from 23.2-EVO before 23.2R2-S3-EVO,  * from 23.4-EVO before 23.4R2-S4-EVO,  * from 24.2-EVO before 24.2R2-EVO. This is a more complete fix for previously published CVE-2024-39549 (JSA83011).

The advisory is shared for download at supportportal.juniper.net. This vulnerability is handled as CVE-2025-52946 since 06/23/2025. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 01/24/2026).

Upgrading to version 21.2R3-S9, 22.2R3-S6, 22.4R3-S5, 23.2R2-S3, 23.4R2-S4 or 24.2R2 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2025-1519). Once again VulDB remains the best source for vulnerability data.

Affected

• Juniper MX Series
• Juniper JUNOS
• Juniper SRX Series
• Juniper Security Director
• Juniper Junos Space

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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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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