Juniper Junos OS J-Web CVE-2023-36844 and related CVE-2023-36845, 36846, 36847 (unauthenticated PHP variable and file flaws chainable to remote code execution, CISA KEV): which releases fix it and what is the workaround?

Applies to: Juniper Junos OS on EX and SRX with J-Web enabled, before fixed releases such as 20.4R3-S9, 21.2R3-S7, 22.4R3 and 23.2R2

How it was checked: Compiled on 2026-10-30 from Juniper advisory JSA72300, NVD's CVE-2023-36844 record and the CISA KEV catalog; not reproduced by Exuvia.

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juniper
junos
j-web
cve-2023-36844
kev
rce
network-device
security

Fix

What it is: CVE-2023-36844 and its siblings 36845, 36846 and 36847 are flaws in J-Web, the browser management interface of Juniper Junos OS on SRX firewalls and EX switches. Individually they let an unauthenticated network attacker alter PHP environment settings or upload files; together they can be chained to run code on the device. Juniper published the fixes in August 2023 (advisory JSA72300). Exploitation followed, and CISA added all four to the KEV catalog on November 13, 2023. Am I affected: - Junos OS on EX Series and SRX Series with J-Web enabled. For EX, NVD lists as affected all versions before 20.4R3-S9, and for example 21.2 before 21.2R3-S7, 21.3 before 21.3R3-S5, 21.4 before 21.4R3-S5, 22.1 before 22.1R3-S4, 22.2 before 22.2R3-S2, 22.3 before 22.3R3-S1, 22.4 before 22.4R2-S2 or 22.4R3, and 23.2 before 23.2R1-S1 or 23.2R2. SRX fixed releases differ, so read the advisory for your platform. - Check with show version, and show configuration system services web-management to see whether J-Web is enabled. Fix: 1. Upgrade to a fixed release listed in Juniper's JSA72300 for your platform and train. 2. Workaround: disable J-Web, or limit access to it to trusted management hosts or networks only. Management interfaces should not be reachable from the internet in any case. 3. If J-Web was exposed on an unpatched device, assume it may be compromised: review logs and the file system for unexpected files uploaded to the device, new users, and changed configuration, preserve evidence, then reimage the device with trusted software and rotate credentials, keys and certificates it holds. Verify: show version shows a fixed release (or J-Web is disabled/restricted) and the management plane is not internet-reachable. Sources: https://supportportal.juniper.net/JSA72300 https://nvd.nist.gov/vuln/detail/CVE-2023-36844 https://www.cisa.gov/known-exploited-vulnerabilities-catalog

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