{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-33774", "assignerOrgId": "8cbe9d5a-a066-4c94-8978-4b15efeae968", "state": "PUBLISHED", "assignerShortName": "juniper", "dateReserved": "2026-03-23T19:46:13.668Z", "datePublished": "2026-04-09T21:34:21.126Z", "dateUpdated": "2026-04-10T14:14:24.774Z" }, "containers": { "cna": { "affected": [ { "defaultStatus": "unaffected", "platforms": [ "MX Series" ], "product": "Junos OS", "vendor": "Juniper Networks", "versions": [ { "lessThan": "23.2R2-S6", "status": "affected", "version": "0", "versionType": "semver" }, { "lessThan": "23.4R2-S7", "status": "affected", "version": "23.4", "versionType": "semver" }, { "lessThan": "24.2R2", "status": "affected", "version": "24.2", "versionType": "semver" }, { "lessThan": "24.4R2", "status": "affected", "version": "24.4", "versionType": "semver" } ] } ], "datePublic": "2026-04-08T16:00:00.000Z", "descriptions": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "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.

On 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'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:


" } ], "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't 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 \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's used in the default RI.\n\nThe issue can be observed with the CLI command:\n\nuser@device> show firewall counter filter \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." } ], "exploits": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "value": "Juniper SIRT is not aware of any malicious exploitation of this vulnerability." } ], "value": "Juniper SIRT is not aware of any malicious exploitation of this vulnerability." } ], "metrics": [ { "cvssV3_1": { "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" }, "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ] }, { "cvssV4_0": { "Automatable": "YES", "Recovery": "USER", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 6.9, "baseSeverity": "MEDIUM", "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/AU:Y/R:U/RE:L", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "LOW", "vulnerabilityResponseEffort": "LOW" }, "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ] } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-754", "description": "CWE-754 Improper Check for Unusual or Exceptional Conditions", "lang": "en", "type": "CWE" } ] } ], "providerMetadata": { "orgId": "8cbe9d5a-a066-4c94-8978-4b15efeae968", "shortName": "juniper", "dateUpdated": "2026-04-09T21:34:21.126Z" }, "references": [ { "tags": [ "vendor-advisory" ], "url": "https://kb.juniper.net/JSA107865" } ], "solutions": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "value": "The following software releases have been updated to resolve this specific issue: 23.2R2-S6, 23.4R2-S7, 24.2R2, 24.4R2, 25.2R1, and all subsequent releases." } ], "value": "The following software releases have been updated to resolve this specific issue: 23.2R2-S6, 23.4R2-S7, 24.2R2, 24.4R2, 25.2R1, and all subsequent releases." } ], "source": { "advisory": "JSA107865", "defect": [ "1855648" ], "discovery": "USER" }, "title": "Junos OS: MX Series: Firewall filters on lo0. in the default routing instance are not in effect", "workarounds": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "value": "Renaming the lo0 logical unit used in the default routing instance from non-0 to 0 resolves this issue.
" } ], "value": "Renaming the lo0 logical unit used in the default routing instance from non-0 to 0 resolves this issue." } ], "x_generator": { "engine": "Vulnogram 0.1.0-dev" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-04-10T14:14:09.835711Z", "id": "CVE-2026-33774", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-10T14:14:24.774Z" } } ] } }