Junos OS (SRX firewalls)
CVE-2026-21903: Subscribing to telemetry sensors at scale causes all FPCs to crash
A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker, authenticated with low privileges to cause a Denial-of-Service (DoS).
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS 0 | 22.4R3-S7 or later |
| Junos OS 23.2 | 23.2R2-S4 or later |
| Junos OS 23.4 | 23.4R2 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker, authenticated with low privileges to cause a Denial-of-Service (DoS).
Subscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart. The issue was not seen when YANG packages for the specific sensors were installed.
This issue affects Junos OS:
- all versions before 22.4R3-S7,
- 23.2 version before 23.2R2-S4,
- 23.4 versions before 23.4R2.
Am I affected?
A device is only exposed to this issue if GRPC services are configured:
[ system services extension-service request-response grpc ]
Workarounds
There are no known workarounds for this issue.
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.