Juniper Junos OS up to 21.2R3-S8 on ACX exceptional condition

Summaryinfo

A vulnerability has been found in Juniper Junos OS up to 21.2R3-S8 on ACX and classified as critical. This vulnerability affects unknown code. This manipulation causes exceptional condition. This vulnerability only affects products that are no longer supported by the maintainer. This vulnerability is registered as CVE-2025-52947. The attack requires access to the local network. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Juniper Junos OS up to 21.2R3-S8 on ACX and classified as critical. Affected by this vulnerability is an unknown part. The manipulation with an unknown input leads to a exceptional condition vulnerability. The CWE definition for the vulnerability is CWE-755. The product does not handle or incorrectly handles an exceptional condition. As an impact it is known to affect availability. The summary by CVE is:

An Improper Handling of Exceptional Conditions vulnerability in route processing of Juniper Networks Junos OS on specific end-of-life (EOL) ACX Series platforms allows an attacker to crash the Forwarding Engine Board (FEB) by flapping an interface, leading to a Denial of Service (DoS). On ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096 devices, FEB0 will crash when the primary path port of the L2 circuit IGP (Interior Gateway Protocol) on the local device goes down. This issue is seen only when 'hot-standby' mode is configured for the L2 circuit. This issue affects Junos OS on ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096:  * all versions before 21.2R3-S9.

The advisory is shared at supportportal.juniper.net. This vulnerability is known as CVE-2025-52947 since 06/23/2025. The exploitation appears to be easy. The attack needs to be done within the local network. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 01/24/2026).

The vulnerability scanner Nessus provides a plugin with the ID 242694 (Juniper Junos OS Vulnerability (JSA100051)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 21.2R3-S9 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (242694) and CERT Bund (WID-SEC-2025-1519). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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

Version

• 21.2R3-S8

License

• commercial

Support

• end of life

Website

• Vendor: https://www.juniper.net/

CPE 2.3info

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CPE 2.2info

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Entryinfo

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