High7.5Juniper Networks

High [CVE-2026-21906] Improper Handling of Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS…

This high-severity Juniper Networks advisory covers CVE-2026-21906 affecting Junos, Junos OS, SRX.

CVE-2026-21906 Published Jan 15, 2026Updated by vendor Jun 17, 2026

CVE-2026-21906

Affected products & platforms

Juniper NetworksSRXFirewallSwitchesJunosEX / QFX Switches

Open vendor advisory

Android app · Google Play

Monitor future Juniper Networks CVEs from your phone.

Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 32 official vendor sources and 160+ reviewed platform categories.

Matching phone alertsOptional email delivery

Get CVE alerts See app features

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 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 23.2 before 23.2R2-S5,
from 23.4 before 23.4R2-S5,

Affected products named by the advisory: EX.

Affected versions

22.4
23.2
23.4
24.2
24.4
25.2
all versions

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Fixed versions

21.4R3-S12
22.4R3-S8
23.2R2-S5
23.4R2-S5
24.2R2-S3
24.4R2-S1
25.2R1-S1

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Mitigation

Upgrade to a fixed release: 21.4R3-S12, 22.4R3-S8, 23.2R2-S5, 23.4R2-S5, 24.2R2-S3, 24.4R2-S1. That is the remediation for this advisory.

The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Sources

Official and corroborating records used to build this advisory.

Juniper SIRT (JSA) via NVDofficial
Official vendor feed — the source of truth for this advisory. VulniPulse polled this feed and parsed this entry from it.
Juniper Networks

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-21906NVD CVE.org MITRE

Official resources

Junos OS software downloads & install/upgrade (target: 21.4R3-S12 / 22.4R3-S8 / 23.2R2-S5)
Official documentation
This advisory names 21.4R3-S12 / 22.4R3-S8 / 23.2R2-S5 as the first fixed releases — official upgrade documentation for Junos OS on SRX / MX / EX / QFX.
Junos OS release & EOL / support dates
Release notes
Confirm your train is still supported and pick a fixed maintenance release.
Juniper Security Advisories portal
Official documentation
Canonical Juniper SIRT advisory portal — search here for the full JSA text and revisions.

Discussion(0)

No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.