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CVE-2026-57054: Junos OS: MX Series: Web filtering doesn't block specifically formatted URLs
- Severity: medium (CVSS 5.8 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.4% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-07-09 · updated 2026-10-25
- Weakness: CWE-706
Description
A Use of Incorrectly-Resolved Name or Reference vulnerability in the URL filtering plugin of Juniper Networks Junos OS on MX Series allows an unauthenticated, network-based attacker to bypass web filtering and access downstream resources that should be unreachable. If an MX Series device is configured with web filtering, and an attacker sends a request with a specifically formatted URL, this request will get forwarded despite the system being configured to block it. In turn, an attacker can access downstream resources that are expected to be unreachable. This issue affects Junos OS on MX Series: * all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S8, * 24.2 versions before 24.2R2-S5, * 24.4 versions before 24.4R2-S4, * 25.2 versions before 25.2R2-S1, * 25.4 versions before 25.4R1-S2, 25.4R2.
Affected products
- Juniper Junos OS: before 23.2; 23.2, 23.2-r1, 23.2-r1-s1, 23.2-r1-s2, 23.2-r2, 23.2-r2-s1 (+42) — fixed in 23.2
How to fix
Upgrade to a fixed version: Juniper Junos OS 23.2. Check the vendor advisory for mitigations.
References
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