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VulnerabilityPublished

CVE-2026-33774: Juniper Networks Junos OS · Unchecked Error Condition

Affects Juniper Networks Junos OSSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium · fixed in 24.4R2 : update Juniper Networks Junos OS when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 24.4R2, 24.2R2, 23.4R2-S7 +1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade Juniper Networks Junos OS to 24.4R2, 24.2R2, 23.4R2-S7 or 23.2R2-S6.

Affected software

ProductAffectedFixed in
Juniper NetworksJunos OSAffected
  • >=24.4 <24.4R2
Fixed in
  • 24.4R2
Juniper NetworksJunos OSAffected
  • >=24.2 <24.2R2
Fixed in
  • 24.2R2
Juniper NetworksJunos OSAffected
  • >=23.4 <23.4R2-S7
Fixed in
  • 23.4R2-S7
Juniper NetworksJunos OSAffected
  • <23.2R2-S6
Fixed in
  • 23.2R2-S6

AI-suggested

The affected Junos OS versions are identified, and fixed versions appear to be 23.2R2-S6 or later, 23.4R2-S7 or later, 24.2R2 or later, and 24.4R2 or later. Until an official patch or update is applied, administrators should avoid applying firewall filters on non-zero loopback interfaces in the default routing instance or consider alternative configurations to mitigate bypass risk. Monitor Juniper Networks advisories for official fixes and guidance.

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 <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

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