CVE-2026-21906: Junos OS: 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.
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.
Affected Software
Remediation
Information
Event History
Frequently Asked Questions
What is the severity of CVE-2026-21906?
CVE-2026-21906 is classified as a critical severity vulnerability affecting Junos OS on SRX Series.
How do I fix CVE-2026-21906?
To mitigate CVE-2026-21906, update your Junos OS to a fixed version 21.4R3-S12 or later.
What impacts does CVE-2026-21906 have on my network?
CVE-2026-21906 can lead to the packet forwarding engine crashing, disrupting network services.
Is CVE-2026-21906 exploitable remotely?
Yes, CVE-2026-21906 can be exploited remotely by sending a specific ICMP packet.
Which devices are affected by CVE-2026-21906?
CVE-2026-21906 affects Juniper Networks SRX Series devices running vulnerable versions of Junos OS.