CVE-2023-36851
MEDIUMCVE-2023-36851 is a medium-severity (CVSS 5.3) Missing Authentication vulnerability in juniper junos. It is in CISA's Known Exploited Vulnerabilities catalog (added 2023-11-13) — treat it as actively exploited and patch now. O3 Security detects and blocks CVE-2023-36851 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
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…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2023-11-13. Federal agencies were required to remediate by 2023-11-17.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2023-36851.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-36851 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
Affected Products
junosjuniperResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every juniper junos deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2023-36851 yet — track the juniper junos advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2023-36851 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2023-36851. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-36851 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2023-36851 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.