CVE-2026-21914: SRX Series: A specifically malformed GTP message will cause an FPC crash

Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.

Affected and fixed versions

Product / branch	Fixed in
Junos OS (SRX Series) 0	22.4R3-S8 or later
Junos OS (SRX Series) 23.2	23.2R2-S5 or later
Junos OS (SRX Series) 23.4	23.4R2-S6 or later
Junos OS (SRX Series) 24.2	24.2R2-S3 or later
Junos OS (SRX Series) 24.4	24.4R2-S2 or later
Junos OS (SRX Series) 25.2	25.2R1-S1, 25.2R2 or later

Always confirm against the vendor advisory, which lists every fixed hotfix.

What it is

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.

Am I affected?

To be exposed to this issue the device needs to be configured with a GTP profile as follows:

[ security policies ... policy <policy-name> then permit application-services gtp-profile <profile-name> ]

Workarounds

There are no known workarounds for this issue.

Exploitation

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.