If left unpatched, CVE-2026-33774 could lead to major system disruptions or data loss.
Status: Awaiting Analysis
Last updated: 🕒 13 Apr 2026, 15:02 UTC
Originally published on: 🕙 09 Apr 2026, 22:16 UTC
Time between publication and last update: 3 days
CVSS Release: version 3
sirt@juniper.net
Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
CVE-2026-33774: 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.
The exploitability of CVE-2026-33774 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
With low attack complexity and no required privileges, CVE-2026-33774 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-33774, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-33774, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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