Juniper Junos OS up to 25.4R1-S1 Http-Gatekeeper out-of-bounds write

Summaryinfo

A vulnerability, which was classified as critical, was found in Juniper Junos OS up to 25.4R1-S1. This affects an unknown function of the component Http-Gatekeeper. Such manipulation leads to out-of-bounds write. This vulnerability is referenced as CVE-2026-57021. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in Juniper Junos OS up to 25.4R1-S1 and classified as critical. Affected by this issue is some unknown functionality of the component Http-Gatekeeper. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is availability. CVE summarizes:

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 compliance check, a network-based attacker sending specifically formatted requests can trigger an out of bounds write leading to an http-gk process crash. This crash leads to unavailability of all services depending on the [ system services web-management ] configuration (like J-Web, remote access VPN and firewall authentication) until the process automatically restarts. This issue affects Junos OS on SRX Series: * 23.2 versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S8, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2-S4, * 25.2 versions before 25.2R2, * 25.4 versions before 25.4R1-S1, 25.4R2.

The advisory is available at supportportal.juniper.net. This vulnerability is handled as CVE-2026-57021 since 06/23/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 07/10/2026).

Upgrading to version 23.2R2-S7, 23.4R2-S8, 24.2R2-S4, 24.4R2-S4, 25.2R2, 25.4R1-S1 or 25.4R2 eliminates this vulnerability.

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Productinfo

Type

• Router Operating System

Vendor

• Juniper

Name

• Junos OS

Version

• 23.2R2-S6
• 23.4R2-S7
• 24.2R2-S3
• 24.4R2-S3
• 25.2R1
• 25.4R1
• 25.4R1-S1

License

• commercial

Website

• Vendor: https://www.juniper.net/

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