VYPR
← All advisories
Medium severity6.5NVD Advisory· Published Apr 9, 2026· Updated Jul 8, 2026

CVE-2026-33774

CVE-2026-33774

Description

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

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.

Affected products

27
  • Juniper Networks/Junos27 versions
    cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*+ 26 more
    • cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*range: <23.2
    • cpe:2.3:o:juniper:junos:23.2:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s5:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s5:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s6:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1:*:*:*:*:*:*
    • (no CPE)range: <23.2R2-S6, 23.4<23.4R2-S7, 24.2<24.2R2, 24.4<24.4R2

Patches

Vulnerability mechanics

References

1

News mentions

0

No linked articles in our index yet.