CVE-2026-57021 in Junos OS
An Out-of-bounds Write vulnerability in the http-gatekeeper (http-gk) of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). If an SRX Series device is configured for remote-access VPN with pre-logon...
Quick answer
Juniper Networks Junos OS should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Junos OS 23.2 to before 23.2R2-S7
- Junos OS 23.4 to before 23.4R2-S8
- Junos OS 24.2 to before 24.2R2-S4
- Junos OS 24.4 to before 24.4R2-S4
- Junos OS 25.2 to before 25.2R2
- Junos OS 25.4 to before 25.4R1-S1, 25.4R2
Fixed versions
- Junos OS 23.2R2-S7 or later
- Junos OS 23.4R2-S8 or later
- Junos OS 24.2R2-S4 or later
- Junos OS 24.4R2-S4 or later
- Junos OS 25.2R2 or later
- Junos OS 25.4R1-S1, 25.4R2
How to fix it
Update Junos OS. The old network OS can allow denial of service, data exposure, or bypass, depending on the CVE.
- Check the exact Juniper platform and release train.
- Upgrade to a fixed release: Junos OS 23.2R2-S7 or later, Junos OS 23.4R2-S8 or later, Junos OS 24.2R2-S4 or later, Junos OS 24.4R2-S4 or later, Junos OS 25.2R2 or later, Junos OS 25.4R1-S1, 25.4R2.
- Follow Juniper maintenance and rollback guidance.
- Watch routing, VPN, flow, CPU, and crash logs after the update.
Scan now. Google sign-in is only needed to unlock fix guidance.
Verify the fix
- Run show version and confirm the fixed Junos release is installed.
- Scan again and confirm CVE-2026-57021 is gone.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-57021?
Juniper Networks Junos OS versions listed as affected should be reviewed: Junos OS 23.2 to before 23.2R2-S7, Junos OS 23.4 to before 23.4R2-S8, Junos OS 24.2 to before 24.2R2-S4, Junos OS 24.4 to before 24.4R2-S4, Junos OS 25.2 to before 25.2R2, Junos OS 25.4 to before 25.4R1-S1, 25.4R2.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.