CVE-2023-36851VulnerabilityPublished 26 Sep 2023Updated 21 Oct 2025

CVE-2023-36851: Juniper Networks Junos OS · Missing Authentication

Affects Juniper Networks Junos OSSource CVE Database V5

Exploited in the wild · KEV due 17 Nov 2023 · 1% EPSS : apply the vendor's fix or mitigations to Juniper Networks Junos OS now.

Data as of 26 Oct 2026, 07:57 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: 1.1% chance of exploitation in 30 days – higher than 66% 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 26 Sep 2023
Detectable: no evidence on record.
No public nuclei template indexed
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 48 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, 91 days before disclosure
CVE published
on cve.org
2023-09-2619:53Z, t = 0
Added to CISA KEV (opens in a new tab)
exploitation confirmed
2023-11-13, 48 days after disclosure
KEV remediation due
US federal deadline
2023-11-17, 52 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 =21.2 =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 Missing Authentication for Critical Function vulnerability in Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause limited impact to the file system integrity. With a specific request to webauth_operation.php that doesn't require authentication, an attacker is able to upload and download arbitrary files via J-Web, leading to a loss of integrity or confidentiality, which may allow chaining to other vulnerabilities. This issue affects Juniper Networks Junos OS on SRX Series: * 21.2 versions prior to 21.2R3-S8; * 21.4 versions prior to 21.4R3-S6; * 22.1 versions prior to 22.1R3-S5; * 22.2 versions prior to 22.2R3-S3; * 22.3 versions prior to 22.3R3-S2; * 22.4 versions prior to 22,4R2-S2, 22.4R3; * 23.2 versions prior to 23.2R1-S2, 23.2R2.

Impact

For European organizations, the impact of CVE-2023-36851 can be substantial, particularly for those relying on Juniper SRX Series devices for perimeter security, VPN termination, and network segmentation. Unauthorized file upload/download can lead to manipulation or theft of configuration files, potentially allowing attackers to alter firewall rules, disable security controls, or exfiltrate sensitive data. This undermines the integrity and confidentiality of network infrastructure, increasing the risk of further exploitation or lateral movement within corporate networks. Critical sectors such as finance, telecommunications, energy, and government agencies in Europe could face operational disruptions or data breaches if exploited. Although availability impact is not directly indicated, integrity loss can indirectly affect service reliability and trustworthiness. The vulnerability's network-based, unauthenticated nature increases the attack surface, especially if J-Web interfaces are exposed or insufficiently segmented. Given the strategic importance of secure network gateways in European cybersecurity frameworks and regulatory environments (e.g., NIS Directive), exploitation could lead to compliance issues and reputational damage.

Mitigation

1. Immediately apply the official Juniper patches corresponding to your Junos OS version as listed in the advisory (e.g., 21.2R3-S8, 21.4R3-S6, 22.1R3-S5, etc.). 2. Restrict access to the J-Web management interface by implementing network segmentation and firewall rules that limit access to trusted administrative hosts only. 3. Disable J-Web management interface if not required or replace it with CLI-based management secured via VPN or dedicated management networks. 4. Monitor network traffic for unusual file upload/download activity targeting webauth_operation.php or other J-Web endpoints. 5. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect exploitation attempts. 6. Conduct regular audits of device configurations and file system integrity to detect unauthorized changes. 7. Educate network administrators on the risks of exposing management interfaces and enforce strong authentication and access control policies. 8. Maintain an incident response plan that includes procedures for containment and remediation of Junos OS compromises.

CWE-306Missing Authentication for Critical Function (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #21OWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
Architecture and Design
Divide the software into anonymous, normal, privileged, and administrative areas. Identify which of these areas require a proven user identity, and use a centralized authentication capability.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Architecture and Design
Where possible, avoid implementing custom, "grow-your-own" authentication routines and consider using authentication capabilities as provided by the surrounding framework, operating system, or environment.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V1.2.3 (opens in a new tab)
V1.2.2 (opens in a new tab)
V1.2.4 (opens in a new tab)
Attack patterns
Choosing Message Identifier (opens in a new tab)
Force the System to Reset Values (opens in a new tab)
Using Unpublished Interfaces or Functionality (opens in a new tab)
Cross Site Request Forgery (opens in a new tab)
Communication Channel Manipulation (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, 20:49 UTC

WeaknessesCWE-306

Technical details

References

Community reviews

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