CVE-2026-21914

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.