Juniper Junos OS up to 25.2R1-S1 on SRX GPRS Tunnelling Protocol locking

Summaryinfo

A vulnerability categorized as critical has been discovered in Juniper Junos OS up to 25.2R1-S1 on SRX. The affected element is an unknown function of the component GPRS Tunnelling Protocol. Such manipulation leads to locking. This vulnerability is listed as CVE-2026-21914. The attack may be performed from remote. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Juniper Junos OS up to 25.2R1-S1 on SRX. It has been rated as critical. Affected by this issue is an unknown functionality of the component GPRS Tunnelling Protocol. The manipulation with an unknown input leads to a locking vulnerability. Using CWE to declare the problem leads to CWE-667. The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors. Impacted is availability. CVE summarizes:

An Improper Locking vulnerability in the GTP plugin of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (Dos). If an SRX Series device receives a specifically malformed GPRS Tunnelling Protocol (GTP) Modify Bearer Request message, a lock is acquired and never released. This results in other threads not being able to acquire a lock themselves, causing a watchdog timeout leading to FPC crash and restart. This issue leads to a complete traffic outage until the device has automatically recovered. This issue affects Junos OS on SRX Series: * all versions before 22.4R3-S8, * 23.2 versions before 23.2R2-S5, * 23.4 versions before 23.4R2-S6, * 24.2 versions before 24.2R2-S3, * 24.4 versions before 24.4R2-S2, * 25.2 versions before 25.2R1-S1, 25.2R2.

The advisory is shared for download at supportportal.juniper.net. This vulnerability is handled as CVE-2026-21914 since 01/05/2026. 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 01/16/2026).

Upgrading to version 22.4R3-S8, 23.2R2-S5, 23.4R2-S6, 24.2R2-S3, 24.4R2-S2, 25.2R1-S1 or 25.2R2 eliminates this vulnerability.

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Productinfo

Type

• Router Operating System

Vendor

• Juniper

Name

• Junos OS

Version

• 22.4R3-S7
• 23.2R2-S4
• 23.4R2-S5
• 24.2R2-S2
• 24.4R2-S1
• 25.2R1
• 25.2R1-S1

License

• commercial

Website

• Vendor: https://www.juniper.net/

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