Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2023-36844

Junos OS

Juniper Networks / Junos OS · affected before 20.4R3-S9

Watch CVE-2023-36844 Browse KEV feed
Severity
CVSS 5.3 · Medium
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
90.0%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2023-36844 is an unauthenticated vulnerability affecting Juniper Networks Junos OS. A PHP External Variable Modification vulnerability in J-Web of Juniper Networks Junos OS on EX Series allows an unauthenticated,...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV. Also confirmed by third-party sources.

Who is affected?

Juniper Networks / Junos OS affected before 20.4r3-s9.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Junos OS

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 Networks Affected
Junos OS
Before 20.4R3-S9 Before 21.1* Before 21.2R3-S6 Before 21.3R3-S5 Before 21.4R3-S5 Before 22.1R3-S4 Before 22.2R3-S2 Before 22.3R3-S1 Before 22.4R2-S2, 22.4R3 Before 23.2R1-S1, 23.2R2
View vendor advisory (opens in new tab)
Published
17 Aug 2023
Exploitation Reported
13 Nov 2023
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

php edge cisa nuclei_scanner

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 13 Nov 2023

A trusted third party reported exploitation.

Proof of concept available

GitHub

Recorded 24 Sep 2023

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CISA First 2023-11-13 00:00 UTC
The Shadowserver 2026-05-29 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-36844.yaml 25 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

5.3 Medium

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

90.0%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

PHP External Variable Modification CWE-473

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Juniper Devices - Remote Code Execution

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 14:20 UTC

    Public PoC available

    Public proof-of-concept code published

  2. 00:00 UTC

    KEV confirmed by The Shadowserver

    Exploitation attested by an external source

  3. 00:00 UTC

    Nuclei template available

    Scanner coverage available

  4. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  5. 19:17 UTC

    CVE published

    Vulnerability disclosed publicly

  6. 16:17 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

Start 14-day Pro trial Read API docs
  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2023-36844

Sample API response 
{
  "cve_id": "CVE-2023-36844",
  "confidence": "Confirmed",
  "cvss_score": 5.3,
  "cvss_estimated": false,
  "epss_score": 0.89958,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}