CVE-2026-21906 - Junos OS Plugin
CVE-2026-21906
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.
CVE-2026-21906
HIGH
CVSS 8.7
Published 2026-01-15
Updated 2026-01-23
AI Risk High (84/100)
Active Exploit: No strong signal
Published Exploit: No public exploit references
Priority: P2 Urgent
Severity Band
HIGH
CVSS Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:M/U:Red
Affected Components
1
Reference Links
3
AI Risk Engine
High (84/100)
Exploitability
High
Active Exploitation
No strong signal
Published Exploit Status
No public exploit references
AI Context
Machine-generated threat intelligence
AI
Updated 12 days ago
AI enriched 12 days ago (2026-04-09 08:01 UTC)
Technical Summary
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…
Potential Impact
Severity is HIGH (CVSS 8.7). Depending on deployment context, affected components may be exposed to unauthorized actions or data integrity risk.
Exploitability Assessment
Exploitability is assessed as High based on low-bar exploit prerequisites.
Primary risk drivers: low-bar exploit prerequisites
Mitigation Recommendations
Validate affected product versions, prioritize patching, and monitor references for vendor remediation guidance. If immediate patching is not possible, apply compensating controls and limit exposure of vulnerable surfaces.
Detection & Monitoring
Track authentication anomalies, unexpected file writes, and suspicious plugin API activity around affected components.
Business Impact Lens
Prioritize remediation where affected components process customer data, admin sessions, or Internet-exposed workflows.
