Juniper · Junos OS
CVE-2023-36844
Junos OS: EX Series: A PHP vulnerability in J-Web allows an unauthenticated attacker to control important environment variables
What it is
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.
CISA: 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.
What to do
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: November 17, 2023
More exploited flaws from Juniper
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Mar 13, 2025 | Improper Isolation or Compartmentalization | Junos OS | Medium 6.7 | 1.7% |
| Nov 13, 2023 | EX Series and SRX Series PHP External Variable Modification | Junos OS | Critical 9.8 | 95% |
| Nov 13, 2023 | SRX Series Missing Authentication for Critical Function | Junos OS | Medium 5.3 | 93% |
| Nov 13, 2023 | EX Series Missing Authentication for Critical Function | Junos OS | Medium 5.3 | 83% |
| Nov 13, 2023 | SRX Series Missing Authentication for Critical Function | Junos OS | Medium 5.3 | 1.1% |
| Mar 25, 2022 | Path Traversal | Junos OS | High 8.8 | 4.9% |
| Oct 2, 2025 | Improper Authentication | ScreenOS | Critical 9.8 | 61% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.