CVE-2026-33774: Juniper Networks Junos OS · Unchecked Error Condition
Affects Juniper Networks Junos OSSource CVE Database V5
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
- 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:NExploitation evidence
Disclosed: evidence found.
CVE published 9 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| Juniper NetworksJunos OS | Affected
| Fixed in
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| Juniper NetworksJunos OS | Affected
| Fixed in
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| Juniper NetworksJunos OS | Affected
| Fixed in
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| Juniper NetworksJunos OS | Affected
| Fixed in
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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.