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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-2023-36851

MEDIUM · 5.3 CVSS v3.1 Published 2023-09-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
In the wild 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 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.

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

Missing authentication in webauth_operation.php in J-Web allows unauthenticated network attackers to upload and download arbitrary files on SRX Series devices, leading to integrity and confidentiality compromise that may enable chaining with other vulnerabilities.

MitigationApply vendor-supplied Junos OS patches for affected versions (21.2R3-S8, 21.4R3-S6, 22.1R3-S5, 22.2R3-S3, 22.3R3-S2, 22.4R2-S2/22.4R3, 23.2R1-S2/23.2R2 or later). If patching is not immediately feasible, consider disabling J-Web or restricting access to trusted networks.

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:= 21.2= 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
None
Integrity
Low
Availability
None

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

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. Confirm device is an SRX Series firewall
    Run 'show chassis hardware' or 'show version' to identify the device model
    Affected if Device is not an SRX model (this vulnerability only affects SRX Series)
  2. Identify installed Junos version
    Run 'show version' and note the exact software version string
    Affected if Version exactly matches 21.2, 21.4, 22.1, 22.2, 22.3, 22.4, or 23.2
  3. Verify J-Web is enabled
    Run 'show system services web-management' to check if J-Web HTTP or HTTPS service is configured and active
    Affected if J-Web is enabled and accessible (vulnerability requires J-Web to be running)
  4. Inspect for vulnerable endpoint exposure
    Check if the URL path /var/www/html/webauth_operation.php exists on the device (this file handles the vulnerable authentication logic)
    Affected if The webauth_operation.php file exists and J-Web is exposed externally or on an accessible network

User is affected if they have an SRX device running an exact affected Junos version (21.2/21.4/22.1/22.2/22.3/22.4/23.2) with J-Web service 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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor-supplied Junos OS patches for affected versions (21.2R3-S8, 21.4R3-S6, 22.1R3-S5, 22.2R3-S3, 22.3R3-S2, 22.4R2-S2/22.4R3, 23.2R1-S2/23.2R2 or later). If patching is not immediately feasible, consider disabling J-Web or restricting access to trusted networks.

Recommended fix High confidence

22.4R3 (or 22.4R2-S2 or later stable release for your branch)

  1. 1. Identify the current Junos OS version running on the SRX device using 'show version' command
  2. 2. Determine the appropriate upgrade path based on current version (upgrade to a fixed release as listed below)
  3. 3. Download the fixed Junos OS software image from Juniper Networks support portal (supportportal.juniper.net)
  4. 4. Transfer the software image to the device using SCP or USB storage
  5. 5. Verify the software package integrity using 'request system software validate <package>' command
  6. 6. Install the software using 'request system software add <package>' command
  7. 7. Reboot the device using 'request system reboot' command
  8. 8. After reboot, verify the new version is installed using 'show version' and confirm the fix is applied
Caveat Standard Junos upgrade considerations apply - review release notes for your version branch for any migration or compatibility notes

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

Fix this in Junos Exploited in the wild — priority engagement
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2023-36851 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