Track vulnerabilities like this one.
Sign up free to get alerted when software you use is affected.
5.3
CVE-2026-57031: Junos OS MX Series: Unsecured Firewall for Some Subscribers
CVE-2026-57031 · published 3 months ago
Summary
A security issue in Junos OS MX Series allows neighboring subscribers to bypass configured firewall rules if they are connected to static interfaces. This affects certain devices and versions, and users should check their configuration and update their software if necessary to prevent unauthorized access.
What to do
- Update juniper networks junos os to version 23.2R2-S7 or later.
Affected software
| Vendor | Product | Affected versions |
|---|---|---|
| juniper networks | junos os | < 23.2R2-S7 |
Original advisory text
An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on MX Series allows adjacent subscribers to bypass configure...
An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on MX Series allows adjacent subscribers to bypass configured firewall filters.
On MX Series devices with MPC10/11, LC4800/9600, and MX304 with subscribers configured on static interfaces, ingress firewall filters are not enforced, so that neither protocol level nor upstream bandwidth limitation are in effect.
This issue affects Junos OS on MX with MPC10/11, LC4800/9600/4802, and MX304:
* 23.2 versions from 23.2R2-S1 before 23.2R2-S7,
* 23.4 versions from 23.4R2 before 23.4R2-S7,
* 24.2 versions before 24.2R2-S3,
* 24.4 versions before 24.4R2-S2,
* 25.2 versions before 25.2R2.
On MX Series devices with MPC10/11, LC4800/9600, and MX304 with subscribers configured on static interfaces, ingress firewall filters are not enforced, so that neither protocol level nor upstream bandwidth limitation are in effect.
This issue affects Junos OS on MX with MPC10/11, LC4800/9600/4802, and MX304:
* 23.2 versions from 23.2R2-S1 before 23.2R2-S7,
* 23.4 versions from 23.4R2 before 23.4R2-S7,
* 24.2 versions before 24.2R2-S3,
* 24.4 versions before 24.4R2-S2,
* 25.2 versions before 25.2R2.
References
- https://supportportal.juniper.net/JSA110091 vendor-advisory
Internet-facing
60 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit
- Gives an attacker partial control
Severity
5.3
Medium
Type
CWE-754Improper Check for Unusual or Exceptional Conditions
Timeline
Published9 Jul 2026
Updated4 Nov 2026
First seen9 Jul 2026
Track software like this
Free during beta