FKIE_CVE-2026-33774
Vulnerability from fkie_nvd - Published: 2026-04-09 22:16 - Updated: 2026-04-09 22:16
Severity ?
Summary
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
Impacted products
| Vendor | Product | Version |
|---|
{
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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.\n\nOn MX platforms with \n\nMPC10, MPC11, LC4800 or LC9600\n\nline cards, and MX304, firewall filters applied on a loopback interface lo0.n (where n is a non-0 number) don\u0027t get executed when lo0.n is in the global VRF / default routing-instance.\n\n An affected configuration would be:\n\nuser@host# show configuration interfaces lo0 | display set\nset interfaces lo0 unit 1 family inet filter input \u003cfilter-name\u003e\n\nwhere 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\u0027s used in the default RI.\n\nThe issue can be observed with the CLI command:\n\nuser@device\u003e show firewall counter filter \u003cfilter_name\u003e \n\nnot showing any matches.\n\nThis issue affects Junos OS on MX Series:\n\n * all versions before 23.2R2-S6,\n * 23.4 versions before 23.4R2-S7,\n * 24.2 versions before 24.2R2,\n * 24.4 versions before 24.4R2."
}
],
"id": "CVE-2026-33774",
"lastModified": "2026-04-09T22:16:25.803",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 2.5,
"source": "sirt@juniper.net",
"type": "Primary"
}
],
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "YES",
"Recovery": "USER",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 6.9,
"baseSeverity": "MEDIUM",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:U/V:X/RE:L/U:X",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "LOW"
},
"source": "sirt@juniper.net",
"type": "Secondary"
}
]
},
"published": "2026-04-09T22:16:25.803",
"references": [
{
"source": "sirt@juniper.net",
"url": "https://kb.juniper.net/JSA107865"
}
],
"sourceIdentifier": "sirt@juniper.net",
"vulnStatus": "Received",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-754"
}
],
"source": "sirt@juniper.net",
"type": "Primary"
}
]
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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