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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Nov 2023.
JunosOperating system · Juniper

CVE-2023-36845

CRITICAL · 9.8 CVSS v3.1 Published 2023-08-17
Fix available
A fix is available. Upgrade to 20.4 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A PHP External Variable Modification vulnerability in J-Web of Juniper Networks Junos OS on EX Series and SRX Series allows an unauthenticated, network-based attacker to remotely execute code. Using a crafted request which sets the variable PHPRC an attacker is able to modify the PHP execution environment allowing the injection und execution of code. This issue affects Juniper Networks Junos OS on EX Series and SRX 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 22.3R2-S2, 22.3R3-S1; * 22.4 versions prior to 22.4R2-S1, 22.4R3; * 23.2 versions prior to 23.2R1-S1, 23.2R2.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

An unauthenticated remote code execution vulnerability in J-Web allows attackers to manipulate the PHPRC PHP environment variable via crafted HTTP requests, enabling arbitrary code execution on affected Juniper EX and SRX series devices.

MitigationUpgrade to a fixed Junos OS version per the vendor advisory (20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R2-S2/22.3R3-S1, 22.4R2-S1/22.4R3, 23.2R1-S1/23.2R2 or later); if patching is delayed, restrict network access to J-Web management interfaces.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JunosOperating system
Affected:< 20.4= 20.4= 21.1= 21.2= 21.3= 21.4= 22.1= 22.2= 22.3= 22.4= 23.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine Junos OS version
    Run 'show version' command on the device CLI to retrieve the installed Junos OS version number
    Affected if The installed version matches any of: < 20.4, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, = 22.2, = 22.3, = 22.4, = 23.2
  2. Confirm device is EX or SRX series
    Run 'show chassis hardware' or 'show system information' to verify the hardware model is from EX Series or SRX Series
    Affected if The device model is EX or SRX series AND the version matches the affected list in step 1
  3. Verify J-Web is enabled
    Run 'show configuration system services web-management' to check if J-Web web management interface is configured and enabled
    Affected if J-Web is enabled (web-management http or https is configured) AND the version is affected from step 1

The environment is affected if the device runs a vulnerable Junos OS version (20.4 through 23.2) on EX or SRX series AND has J-Web web management interface enabled

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 20.4 or later
Fixed in 20.4
Interim mitigation

Upgrade to a fixed Junos OS version per the vendor advisory (20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R2-S2/22.3R3-S1, 22.4R2-S1/22.4R3, 23.2R1-S1/23.2R2 or later); if patching is delayed, restrict network access to J-Web management interfaces.

Recommended fix High confidence

Upgrade to 20.4R3-S9 or later (22.4R3 or 23.2R2 recommended for latest fixes)

  1. Identify current Junos OS version using 'show version' command
  2. Download the appropriate fixed release for your platform (EX Series or SRX Series) from Juniper Networks support portal
  3. Upgrade Junos OS to a fixed version: 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R3, or 23.2R2
  4. Apply upgrade via 'request system software add' command or through J-Web interface
  5. Reboot the device after successful upgrade
  6. Verify new version is running with 'show version'
  7. Disable J-Web interface if not needed using 'set system services web-management http disable' as an additional hardening measure
Caveat Review Juniper release notes for your current version for any compatibility notes; some upgrades may require intermediate steps

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-36845 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data