Junos OS (SRX firewalls)
CVE-2026-21906: SRX Series: With GRE performance acceleration enabled, receipt of a specific ICMP packet causes the PFE to crash
An Improper Handling of Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on SRX Series allows an unauthenticated network-based attacker sending a specific ICMP packet through a GRE tunnel to cause the PFE to crash and restart.
Published
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 | 21.4R3-S12 or later |
| Junos OS (SRX Series) 22.4 | 22.4R3-S8 or later |
| Junos OS (SRX Series) 23.2 | 23.2R2-S5 or later |
| Junos OS (SRX Series) 23.4 | 23.4R2-S5 or later |
| Junos OS (SRX Series) 24.2 | 24.2R2-S3 or later |
| Junos OS (SRX Series) 24.4 | 24.4R2-S1 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 Handling of Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on SRX Series allows an unauthenticated network-based attacker sending a specific ICMP packet through a GRE tunnel to cause the PFE to crash and restart.
When PowerMode IPsec (PMI) and GRE performance acceleration are enabled and the device receives a specific ICMP packet, a crash occurs in the SRX PFE, resulting in traffic loss. PMI is enabled by default, and GRE performance acceleration can be enabled by running the configuration command shown below. PMI is a mode of operation that provides IPsec performance improvements using Vector Packet Processing.
Note that PMI with GRE performance acceleration is only supported on specific SRX platforms. This issue affects Junos OS on the SRX Series:
- all versions before 21.4R3-S12,
- from 22.4 before 22.4R3-S8,
- from 23.2 before 23.2R2-S5,
- from 23.4 before 23.4R2-S5,
- from 24.2 before 24.2R2-S3,
- from 24.4 before 24.4R2-S1,
- from 25.2 before 25.2R1-S1, 25.2R2.
Am I affected?
This issue requires GRE performance acceleration to be enabled:
[set security flow gre-performance-acceleration]
Workarounds
* Disable GRE performance acceleration via 'deactivate security flow gre-performance-acceleration' or * Disable PMI:via 'set security flow power-mode-disable'
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.