CVE-2026-57021: 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

mediumCVSS 5.3CVE-2026-57021

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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: medium — CVSS 5.3
Published: 2026-07-09
Last updated: 2026-07-10
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-57021

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-570210.47% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 38% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-57021	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[NEW] [high] Juniper JUNOS and JUNOS Evolved: Multiple vulnerabilitiescert-bund
unknownJuniper Junos OS Multiple Vulnerabilitieshkcert
unknownMultiple vulnerabilities in Juniper Networks products (July 09, 2026)cert-fr-avis

Recent advisories for An Out-of-bounds Write

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-55233: OpenResty is a high performance web platform. From 1.29.2.1 to before 1.29.2.5, an out-of-boun…nvd · 2026-07-10
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unknownCVE-2026-21048: Out-of-bounds write in parsing DNG format in libimagecodec.media.quram.so prior to SMR Jul-202…nvd · 2026-07-10
unknownCVE-2026-21045: Out-of-bounds write in parsing TIFF format in libimagecodec.media.quram.so prior to SMR Jul-20…nvd · 2026-07-10