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Vulnerabilities

Vulnerability · 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-base

Published Jan 15, 2026 · catalog updated Jan 16, 2026 · Juniper Networks Junos OS

Last checked Oct 30, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21906. EPSS is 0.54%. Act only if a listed version of Juniper Networks Junos OS is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High8.7
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.54%
Remediation
Version ranges on file
Affected products
vendor Juniper Networks Junos OS 23.4 <23.4R2-S5

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 o

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Juniper Networks Junos OS 23.4 <23.4R2-S523.4 <23.4R2-S5

How to fix CVE-2026-21906

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-21906. EPSS is 0.54%. Act only if a listed version of Juniper Networks Junos OS is installed.

Which versions are affected?

Compare what you have installed with Juniper Networks Junos OS 23.4 <23.4R2-S5 23.4 <23.4R2-S5. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.54%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Juniper Junos OS security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jan 15, 2026 · EUVD

    Detected

    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

  2. Jan 16, 2026 · EUVD

    Updated

    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

Sources

  • CVE.orgVulnerability recordCVE-2026-21906

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21906

    30-day exploitation probability 0.54%

    first.org
  • EUVDVulnerability recordEUVD-2026-2698

    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

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 30, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgOct 30, 2026
  • FIRST EPSSOct 30, 2026
  • EUVDOct 30, 2026