CVE-2023-36844: Juniper Junos OS EX Series PHP External Variable Modification Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 13 Nov 2023, 88 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 90%
EPSS score, percentile 99.8 of all scored records
- How severe?
- 5.3 Medium
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline 17 Nov 2023. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Which versions are affected?
Affected
- before 20.4R3-S9
- 21.1
- from 21.2 to before 21.2R3-S6
- from 21.3 to before 21.3R3-S5
- from 21.4 to before 21.4R3-S5
- from 22.1 to before 22.1R3-S4
and 4 more in the table below
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: 17 November 2023.
Solution (from the CVE record)
The following software releases have been updated to resolve this specific issue: 20.4R3-S9*, 21.2R3-S7*, 21.3R3-S5*, 21.4R3-S5*, 22.1R3-S4*, 22.2R3-S2, 22.3R3-S1*, 22.4R2-S2*, 22.4R3*, 23.2R1-S1, 23.2R2*, 23.4R1*, and all subsequent releases. *Pending Publication
Workaround (from the CVE record)
Disable J-Web, or limit access to only trusted hosts.
Advisories and patches
Linked from CISA's catalog entry
- https://supportportal.juniper.net/s/article/2023-08-Out-of-Cycle-Security-Bulletin-Junos-OS-SRX-Series-and-EX-Series-Multiple-vulnerabilities-in-J-Web-can-be-combined-to-allow-a-preAuth-Remote-Code-Execution?language=en_US
- https://nvd.nist.gov/vuln/detail/CVE-2023-36844
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | before 20.4R3-S9 |
| Affected | 21.1 |
| Affected | from 21.2 to before 21.2R3-S6 |
| Affected | from 21.3 to before 21.3R3-S5 |
| Affected | from 21.4 to before 21.4R3-S5 |
| Affected | from 22.1 to before 22.1R3-S4 |
| Affected | from 22.2 to before 22.2R3-S2 |
| Affected | from 22.3 to before 22.3R3-S1 |
| Affected | from 22.4 to before 22.4R2-S2, 22.4R3 |
| Affected | from 23.2 to before 23.2R1-S1, 23.2R2 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
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.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2023-36844 to its Known Exploited Vulnerabilities (KEV) catalog on 13 Nov 2023.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 17 Nov 2023.
- The CVE record was published on 17 Aug 2023, 88 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 5.3 (Medium), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 90% (percentile 99.8), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
Junos OS: EX Series: A PHP vulnerability in J-Web allows an unauthenticated attacker to control important environment variables
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-473: PHP External Variable Modification
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 17 Aug 2023 | CVE record published |
| 13 Nov 2023 | Added to CISA KEV |
| 17 Nov 2023 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited Juniper vulnerabilities
- CVE-2015-7755: Juniper ScreenOS Improper Authentication Vulnerability
- CVE-2025-21590: Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability
- CVE-2023-36845: Juniper Junos OS EX Series and SRX Series PHP External Variable Modification Vulnerability
- CVE-2023-36846: Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability
- CVE-2023-36847: Juniper Junos OS EX Series Missing Authentication for Critical Function Vulnerability
- CVE-2023-36851: Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability