CVE-2023-36844VulnerabilityPublished 17 Aug 2023Updated 21 Oct 2025

CVE-2023-36844: Juniper Networks Junos OS · PHP External Variable Modification

Affects Juniper Networks Junos OSSource CVE Database V5

Exploited in the wild · KEV due 17 Nov 2023 · public detection template (Nuclei) · 89% EPSS : apply the vendor's fix or mitigations to Juniper Networks Junos OS now.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

KEV deadline: 17 Nov 2023 US federal agencies must patch by this date; a sensible deadline for everyone else.
EPSS: 89.9% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

Disclosed: evidence found.
CVE published 17 Aug 2023
Detectable: evidence found.
nuclei template: Juniper Devices - Remote Code Execution
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 88 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

CVE ID reserved
by juniper
2023-06-2716:17Z, 51 days before disclosure
CVE published
on cve.org
2023-08-1719:17Z, t = 0
Added to CISA KEV (opens in a new tab)
exploitation confirmed
2023-11-13, 88 days after disclosure
KEV remediation due
US federal deadline
2023-11-17, 92 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

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

Affected software

Product	Affected	Fixed in
Juniper Networks Junos OS	Affected =0 =21.1 =21.2 =21.3 =21.4 =22.1 =22.2 =22.3 =22.4 =23.2	Fixed in–

Check the firmware or software version for Juniper Networks Junos OS in the device's admin interface against the vendor advisory.

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.

Impact

For European organizations, this vulnerability poses a risk primarily to network infrastructure relying on Juniper EX Series switches running vulnerable Junos OS versions. The partial integrity loss could allow attackers to alter device configurations or interfere with network management processes, potentially disrupting network operations or enabling lateral movement within corporate networks. While confidentiality and availability impacts are not directly indicated, the ability to chain this vulnerability with others could escalate the threat, leading to more severe consequences such as unauthorized access or denial of service. Critical sectors in Europe, including finance, telecommunications, and government, often depend on Juniper networking equipment, making them potential targets. The unauthenticated, network-based nature of the attack increases the risk of exploitation from both external and internal threat actors. Given the widespread use of Juniper devices in European enterprise and service provider networks, failure to address this vulnerability could lead to compromised network integrity and increased exposure to advanced persistent threats.

Mitigation

European organizations should immediately identify all Juniper EX Series devices running affected Junos OS versions through asset inventories and network scans. Applying the latest Junos OS patches that address CVE-2023-36844 is critical; organizations should upgrade to versions at or beyond the fixed releases (e.g., 20.4R3-S9, 21.2R3-S7, 23.2R1-S1, etc.). Until patches are applied, restricting access to the J-Web management interface via network segmentation, firewall rules, or VPNs can reduce exposure. Disabling the J-Web interface if not required or replacing it with CLI-based management can further mitigate risk. Monitoring network traffic for unusual or malformed HTTP requests targeting the J-Web interface may help detect exploitation attempts. Implementing strict access controls and multi-factor authentication for management interfaces, even though this vulnerability does not require authentication, adds defense in depth. Regularly reviewing Juniper security advisories and maintaining up-to-date device firmware will help prevent exploitation of this and related vulnerabilities. Finally, conducting penetration testing and vulnerability assessments focused on network management interfaces can identify residual risks.

CWE-473PHP External Variable Modification (opens in a new tab)
Variant weakness
A PHP application does not properly protect against the modification of variables from external sources, such as query parameters or cookies. This can expose the application to numerous weaknesses that would not exist otherwise.
Requirements · Implementation
Carefully identify which variables can be controlled or influenced by an external user, and consider adopting a naming convention to emphasize when externally modifiable variables are being used. An application should be reluctant to trust variables that have been initialized outside of its trust boundary.
Attack patterns
Manipulating User-Controlled Variables (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

Timeline

What to do

Affected software

Description

AI analysisMachine-generated, updated 21 Oct 2025, 20:48 UTC

Public exploits and detectiona Nuclei detection template

WeaknessesCWE-473

Technical details

References

Community reviews

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