Junos OS (SRX firewalls)
CVE-2025-52947: ACX Series: When 'hot-standby' mode is configured for an L2 circuit, interface flap causes the FEB to crash
An Improper Handling of Exceptional Conditions vulnerability in route processing of Juniper Networks Junos OS on specific end-of-life (EOL) ACX Series platforms allows an attacker to crash the Forwarding Engine Board (FEB) by flapping an interface, leading to 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 (ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, ACX5096) 0 | 21.2R3-S9 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
An Improper Handling of Exceptional Conditions vulnerability in route processing of Juniper Networks Junos OS on specific end-of-life (EOL) ACX Series platforms allows an attacker to crash the Forwarding Engine Board (FEB) by flapping an interface, leading to a Denial of Service (DoS).
On ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096 devices, FEB0 will crash when the primary path port of the L2 circuit IGP (Interior Gateway Protocol) on the local device goes down. This issue is seen only when 'hot-standby' mode is configured for the L2 circuit.
This issue affects Junos OS on ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096:
- all versions before 21.2R3-S9.
Am I affected?
This issue only occurs when an L2 circuit is configured for hot-standby. For example:
[protocols l2circuit neighbor x.x.x.x interface <intf> backup-neighbor x.x.x.x hot-standby]
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.