Vulnerability Description
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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Juniper | Junos | < 21.4 |
| Juniper | Srx1500 | - |
| Juniper | Srx1600 | - |
| Juniper | Srx2300 | - |
| Juniper | Srx300 | - |
| Juniper | Srx320 | - |
| Juniper | Srx340 | - |
| Juniper | Srx345 | - |
| Juniper | Srx380 | - |
| Juniper | Srx4100 | - |
| Juniper | Srx4120 | - |
| Juniper | Srx4200 | - |
| Juniper | Srx4300 | - |
| Juniper | Srx4600 | - |
| Juniper | Srx4700 | - |
| Juniper | Srx5400 | - |
| Juniper | Srx5600 | - |
| Juniper | Srx5800 | - |
Related Weaknesses (CWE)
References
- https://kb.juniper.net/JSA106005Vendor Advisory
- https://supportportal.juniper.net/JSA106005Vendor Advisory
- https://www.juniper.net/documentation/us/en/software/junos/vpn-ipsec/topics/topiTechnical Description
FAQ
What is CVE-2026-21906?
CVE-2026-21906 is a vulnerability with a CVSS score of 7.5 (HIGH). 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...
How severe is CVE-2026-21906?
CVE-2026-21906 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-21906?
Check the references section above for vendor advisories and patch information. Affected products include: Juniper Junos, Juniper Srx1500, Juniper Srx1600, Juniper Srx2300, Juniper Srx300.