An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, network-based attacker to bypass the configured firewall filter and access the control-plane of the device.
On MX platforms with
MPC10, MPC11, LC4800 or LC9600
line cards, and MX304, firewall filters applied on a loopback interface lo0.n (where n is a non-0 number) don't get executed when lo0.n is in the global VRF / default routing-instance.
An affected configuration would be:
user@host# show configuration interfaces lo0 | display set
set interfaces lo0 unit 1 family inet filter input <filter-name>
where a firewall filter is applied to a non-0 loopback interface, but that loopback interface is not referred to in any routing-instance (RI) configuration, which implies that it's used in the default RI.
The issue can be observed with the CLI command:
user@device> show firewall counter filter <filter_name>
not showing any matches.
This issue affects Junos OS on MX Series:
* all versions before 23.2R2-S6,
* 23.4 versions before 23.4R2-S7,
* 24.2 versions before 24.2R2,
* 24.4 versions before 24.4R2.
References
| Link | Resource |
|---|---|
| https://kb.juniper.net/JSA107865 | Vendor Advisory |
Configurations
Configuration 1 (hide)
| AND |
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History
26 Oct 2026, 21:10
| Type | Values Removed | Values Added |
|---|---|---|
| Summary |
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Information
Published : 2026-04-09 22:16
Updated : 2026-10-26 21:10
NVD link : CVE-2026-33774
Mitre link : CVE-2026-33774
CVE.ORG link : CVE-2026-33774
JSON object : View
Products Affected
juniper
- mx304
- junos
- mpc11
- lc4800
- mpc10
CWE
CWE-754
Improper Check for Unusual or Exceptional Conditions