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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 4 May 2026. Known ransomware use
Papercut MfApplication · Papercut

CVE-2023-27351

HIGH · 7.5 CVSS v3.1 Published 2023-04-20
Fix available
A fix is available. Upgrade to 20.1.7 / 21.2.11 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Ransomware High EPSS 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
This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

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

PaperCut NG 22.0.5 contains an authentication bypass vulnerability in the SecurityRequestFilter class due to improper implementation of the authentication algorithm. Remote unauthenticated attackers can exploit this to gain unauthorized access to the system.

MitigationApply the vendor patch or upgrade to a patched version of PaperCut NG that addresses this authentication bypass in the SecurityRequestFilter class.

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
Papercut MfApplication
Affected:>= 15.0, < 20.1.7>= 21.0.0, < 21.2.11>= 22.0.0, < 22.0.9
Papercut NgApplication
Affected:>= 15.0, < 20.1.7>= 21.0.0, < 21.2.11>= 22.0.0, < 22.0.9

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
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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. Identify installed PaperCut version
    Locate the version number in the PaperCut administration interface (typically at the bottom of the dashboard) or check the application log files for version information
    Affected if The displayed version falls within any of these ranges: 15.0 to 20.1.6, 21.0.0 to 21.2.10, or 22.0.0 to 22.0.8
  2. Confirm product type
    Verify whether the installation is PaperCut NG or PaperCut MF
    Affected if The product is PaperCut NG or PaperCut MF and the version matches the affected ranges listed above
  3. Assess network exposure
    Determine if the PaperCut server is accessible from untrusted networks (internet or guest VLANs)
    Affected if The PaperCut web interface is exposed to networks without authentication-gateway restrictions
  4. Verify authentication mechanism
    Review the SecurityRequestFilter configuration in the application logs or admin panel to confirm authentication is enforced
    Affected if Authentication can be bypassed or the SecurityRequestFilter is not properly rejecting unauthenticated requests

A user is affected if they are running PaperCut NG or MF version 15.0-20.1.6, 21.0.0-21.2.10, or 22.0.0-22.0.8 with network accessibility to untrusted clients.

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 20.1.7 / 21.2.11 / 22.0.9 or later
Fixed in 20.1.721.2.1122.0.9
Interim mitigation

Apply the vendor patch or upgrade to a patched version of PaperCut NG that addresses this authentication bypass in the SecurityRequestFilter class.

Recommended fix High confidence

PaperCut MF/NG 22.0.9 or later (or latest stable 22.x release)

  1. 1. Identify the currently installed PaperCut MF or NG version by accessing the PaperCut admin console or checking the server configuration.
  2. 2. Determine which version branch is currently in use (15.x-19.x, 20.x, 21.x, or 22.x).
  3. 3. Download the appropriate fixed version from the official PaperCut website: upgrade to 20.1.7 or later for 20.x branch, 21.2.11 or later for 21.x branch, or 22.0.9 or later for 22.x branch.
  4. 4. Before upgrading, backup the PaperCut database and configuration files as a precautionary measure.
  5. 5. Apply the upgrade following the standard PaperCut upgrade procedure documented in the vendor's installation/upgrade guide.
  6. 6. After upgrade, verify the SecurityRequestFilter class has been updated by confirming the version number in the admin console.
  7. 7. Test authentication functionality to ensure the bypass vulnerability is remediated and legitimate authentication works correctly.
Caveat Review PaperCut release notes for any configuration or feature changes between your current version and the upgrade target; standard upgrade procedures apply

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

Fix this in Papercut Mf Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
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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-2023-27351 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