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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-2023-36844

MEDIUM · 5.3 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 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.

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

PHP External Variable Modification vulnerability in J-Web component of Juniper Junos OS on EX Series allows an unauthenticated network attacker to modify certain PHP environment variables via crafted requests, potentially enabling chaining to other vulnerabilities for further exploitation.

MitigationApply vendor patches for affected versions (20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R2-S2/22.4R3, 23.2R1-S1/23.2R2) or upgrade to a patched release; consider disabling J-Web if not needed.

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
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 EX Series hardware and Junos OS
    Run 'show version' or 'show chassis hardware' to identify the device model. Verify it is an EX Series switch running Junos OS.
    Affected if Device is an EX Series switch running Junos OS
  2. Identify installed Junos OS version
    Run 'show version' and locate the Junos OS version string (for example, 21.2R1.5).
    Affected if Version matches < 20.4, = 20.4, = 21.1, = 21.2, = 21.3, = 21.4, = 22.1, = 22.2, = 22.3, = 22.4, or = 23.2
  3. Determine if J-Web interface is enabled
    Run 'show configuration system services web-management' or check the configuration for 'set system services web-management' statements. J-Web is typically accessible on HTTP/HTTPS ports.
    Affected if J-Web is enabled and accessible via network
  4. Verify J-Web is reachable over network
    Attempt to access the J-Web interface URL (typically https://<device-ip>/) from a network perspective, or check listening ports with 'show system services web-management http' or 'show system services web-management https'.
    Affected if J-Web interface responds to network requests on HTTP or HTTPS

If the device is an EX Series running a Junos OS version in the affected list AND J-Web is enabled and network-accessible, the environment is likely affected by this vulnerability.

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

Apply vendor patches for affected versions (20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R2-S2/22.4R3, 23.2R1-S1/23.2R2) or upgrade to a patched release; consider disabling J-Web if not needed.

Recommended fix High confidence

20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R2-S2/22.4R3, or 23.2R1-S1/23.2R2 (depending on current branch)

  1. 1. Identify the current Junos OS version running on the EX Series device using 'show version' command
  2. 2. Based on the current version, determine the appropriate fixed release from the following options:
  3. - For 20.4.x versions: upgrade to 20.4R3-S9 or later
  4. - For 21.1.x versions: upgrade to 21.1R3-S9 or later (or migrate to a later branch)
  5. - For 21.2.x versions: upgrade to 21.2R3-S7 or later
  6. - For 21.3.x versions: upgrade to 21.3R3-S5 or later
  7. - For 21.4.x versions: upgrade to 21.4R3-S5 or later
  8. - For 22.1.x versions: upgrade to 22.1R3-S4 or later
Caveat Standard Junos upgrade considerations apply - review release notes for your specific version for any hardware compatibility or configuration changes; typically safe within same major version branch

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
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2023-36844 in production — separate from our analysis above.

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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