Exploited

CVE-2023-36844

Juniper Junos OS · Switches, routers and SD-WAN

Juniper Junos OS EX Series PHP External Variable Modification Vulnerability

At a glance

Exploited. Added to CISA’s catalog of exploited vulnerabilities on November 13, 2023.

Affected product: Juniper Junos OS (category Switches, routers and SD-WAN, indicative classification). Name in CISA’s catalog: Juniper Junos OS.

What should I do?

Apply the patches or mitigations from Juniper; if none are available, stop using the product.

Deadline set by CISA for US federal agencies: 4 days (due November 17, 2023). It only binds those agencies, but it is a useful measure of urgency.

Juniper security advisories page (general page, not the advisory for this vulnerability)
The vendor’s specific advisory is listed in the NVD references: CVE-2023-36844 on the NVD website.

Original text of the required action (CISA)

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Timeline

August 17, 2023 Vulnerability published Publication date (NVD)
November 13, 2023 Exploitation confirmed Added to CISA’s KEV catalog
November 17, 2023 CISA deadline Remediation deadline set for US federal agencies

The facts, with their sources

Exploitation confirmed: Yes, on November 13, 2023 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Ransomware: No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Hunt for compromise: Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA required action: Apply the patches or mitigations from Juniper; if none are available, stop using the product. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA deadline: November 17, 2023, 4 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Vulnerability published: August 17, 2023 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Product according to CISA: Juniper Junos OS Filed by this site under “Switches, routers and SD-WAN” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC

Severity and activity

5.3 / 10 CVSS severity: medium

Score from the NVD. Collected Sep 29, 2026.

— Probability of exploitation in the next 30 days (EPSS)

FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.

Description

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.

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 from CISA (KEV catalog).

CERT-FR advisories

No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.

Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.

Sources for this page

CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
NVD (NIST): CVSS severity, publication date, description, vendor references.
EPSS (FIRST): probability of exploitation.
CERT-FR: advisories and alerts (in French).
Brand and category: indicative classification by this site (method).