IRONSMITHINTEL
MEDIUMCVSS5.3
|
Actively Exploited
|CISA KEV|CVE-2023-36844|Auth: none — unauthenticated|Reboot: required|Manual only

Juniper Junos OS EX Series PHP External Variable Modification Vulnerability (CVE-2023-36844)

Juniper Junos OS on EX Series contains a PHP external variable modification vulnerability that allows an unauthenticated, network-based attacker to control certain, important environment variables. Using a crafted request an attacker is able to modify certain PHP environment variables, leading to partial loss of integrity, which may allow chaining to other vulnerabilities.

Published Aug 17, 2023 · Updated May 17, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve partial data exposure, partial data tampering. Federal agencies are required to remediate by 2023-11-17 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-473) (CWE-473) vulnerability in Juniper Junos OS. A PHP External Variable Modification vulnerability in J-Web of Juniper Networks Junos OS on EX Series allows an unauthenticated, network-based attacker to control certain, important environment variables. Using a crafted request an attacker is able to modify certain PHP environment variables leading to partial loss of integrity, which may allow chaining to other vulnerabilities. This issue affects Juniper Networks Junos OS on EX Series: * All versions prior to 20.4R3-S9; * 21.1 versions 21.1R1 and later; * 21.2 versions prior to 21.2R3-S7; * 21.3 versions prior to 21.3R3-S5; * 21.4 versions prior to 21.4R3-S5; * 22.1 versions prior to 22.1R3-S4; * 22.2 versions prior to 22.2R3-S2; * 22.3 versions prior to 22.3R3-S1; * 22.4 versions prior to 22.4R2-S2, 22.4R3; * 23.2 versions prior to 23.2R1-S1, 23.2R2. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

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Phishing link

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Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●Network Security Team
●Firewall Administrators
●IT Security
●Running junos: v < 20.4, 20.4, 21.1, 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, 22.4, 23.2
Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/174865/Juniper-SRX-Firewall-EX-Switch-Remote-Code-Execution.html

How to patch

Manual remediation steps

1
Identify affected hosts: query inventory for network-security installs in scope.
2
Apply the vendor security update referenced in CVE-2023-36844's advisory. No specific KB/version is encoded yet — consult the linked MSRC/vendor URL.
3
Verify the fix per the vendor's published verification steps.
4
Document the remediation in your change ticket and re-scan with your vulnerability scanner to confirm closure.
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2023-36844↗ MSRC Advisory↗ NVD↗ Vendor Advisory