Junos
CVE-2026-21906
HIGH
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Juniper Junos OS SRX Series suffers a denial of service vulnerability in the packet forwarding engine when PowerMode IPsec and GRE performance acceleration are both enabled, allowing remote attackers to crash the device by sending a specially crafted ICMP packet through a GRE tunnel. The crash results in immediate traffic loss and device restart, affecting systems with both features active on vulnerable SRX platforms. No patch is currently available.
Technical ContextAI
Classified as CWE-755 (Improper Handling of Exceptional Conditions). Affects Junos. 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 perf
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
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Same technique Denial Of Service
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External POC / Exploit Code
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