Exploited vulnerability · CISA KEV

Is CVE-2023-36851 exploited? Yes: in CISA KEV since 13 Nov 2023

Gociux · Juniper Junos OS · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2023-36851, Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 13 Nov 2023, 48 days after it was published. It affects Juniper Junos OS, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

What it is

Juniper Junos OS on SRX Series contains a missing authentication for critical function vulnerability that 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 arbitrary files via J-Web, leading to a loss of integrity for a certain part of the file system, which may allow chaining to other vulnerabilities.

What to do

1. Check whether you run it. Look for Junos OS in your asset inventory, including appliances and cloud images. Stack check lists every exploited Juniper CVE at once.
2. Apply the fix. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 26 Sep 2023.
4. Get told next time. Email alerts when CISA adds a CVE for Juniper.

Other exploited CVEs in Junos OS

• CVE-2025-21590: Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability (13 Mar 2025)
• CVE-2023-36844: Juniper Junos OS EX Series PHP External Variable Modification Vulnerability (13 Nov 2023)
• CVE-2023-36845: Juniper Junos OS EX Series and SRX Series PHP External Variable Modification Vulnerability (13 Nov 2023)
• CVE-2023-36846: Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability (13 Nov 2023)
• CVE-2023-36847: Juniper Junos OS EX Series Missing Authentication for Critical Function Vulnerability (13 Nov 2023)
• CVE-2020-1631: Juniper Junos OS Path Traversal Vulnerability (25 Mar 2022)

References

• supportportal.juniper.net/s/article/2023-08-Out-of-Cycle-Security-Bulletin-Junos-OS-S
• nvd.nist.gov/vuln/detail/CVE-2023-36851

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2023 · Juniper scorecard · act-now radar.