Answer in brief
CVE-2026-33774 records a Medium severity (CVSS 6.5) vulnerability in Junos OS: MX Series: Firewall filters on lo0.<non-0> in the default routing instance are not in effect. The current sources do not mark it as known exploited. The current feed maps Juniper Networks/Junos OS (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Juniper Networks/Junos OS (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Juniper Networks/Junos OSgeneric | >=0 <23.2R2-S6 || >=23.4 <23.4R2-S7 || >=24.2 <24.2R2 || >=24.4 <24.4R2 | 23.2R2-S6, 23.4R2-S7, 24.2R2, 24.4R2 |
Published upstream
Apr 9, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 8, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 8, 2026
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.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-33774 records a Medium severity (CVSS 6.5) vulnerability in Junos OS: MX Series: Firewall filters on lo0.<non-0> in the default routing instance are not in effect. The current sources do not mark it as known exploited. The current feed maps Juniper Networks/Junos OS (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Juniper Networks/Junos OS (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Juniper Networks/Junos OSgeneric | >=0 <23.2R2-S6 || >=23.4 <23.4R2-S7 || >=24.2 <24.2R2 || >=24.4 <24.4R2 | 23.2R2-S6, 23.4R2-S7, 24.2R2, 24.4R2 |
Published upstream
Apr 9, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 8, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 8, 2026
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.
Quoted source text, attributed separately from HOL analysis.