CVE-2023-27350
About
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 SetupCompleted class. The issue results from improper access control. An attacker can leverage this vulnerability to bypass authentication and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-18987.
Rainforest analyst review
The vulnerability is an improper access-control flaw in PaperCut NG/MF's SetupCompleted page. The application fails to properly restrict access to setup functionality, so an unauthenticated attacker can navigate directly to that flow, bypass authentication, and reach administrative configuration. From the admin context the attacker abuses PaperCut's built-in scripting and print-script features to run arbitrary commands, and because the PaperCut service typically runs as SYSTEM on Windows, that means full system-level code execution.
PaperCut is print-management software installed on print servers across universities, schools, government, and enterprises, machines that sit inside the network and are trusted but rarely watched closely. Exploitation was fast and broad: ransomware affiliates including Clop and LockBit, along with state-linked actors, weaponized it for initial access, and it landed on CISA's KEV list. Patch to a fixed PaperCut version without delay, and because the exploitation window opened before many organizations patched, restrict the web management port to trusted hosts and hunt for unexpected child processes spawned by the PaperCut service rather than assuming the update alone means you were not already touched.
References
- http://packetstormsecurity.com/files/171982/PaperCut-MF-NG-Authentication-Bypass-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/172022/PaperCut-NG-MG-22.0.4-Authentication-Bypass.html
- http://packetstormsecurity.com/files/172512/PaperCut-NG-MG-22.0.4-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/172780/PaperCut-PaperCutNG-Authentication-Bypass.html
- https://news.sophos.com/en-us/2023/04/27/increased-exploitation-of-papercut-drawing-blood-around-the-internet/
- https://www.papercut.com/kb/Main/PO-1216-and-PO-1219
- https://www.zerodayinitiative.com/advisories/ZDI-23-233/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27350
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Frequently asked questions
What is CVE-2023-27350?
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 SetupCompleted class. The issue results from improper access control.
How severe is CVE-2023-27350?
CVE-2023-27350 carries a CVSS 3.1 base score of 9.8, rated critical. On the Rainforest Risk Index — which weighs the severity alongside how easy the flaw is to reach and how broad its impact is — it scores 99 out of 100, in the critical band.
How is CVE-2023-27350 exploited?
According to the CVSS vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H): attack vector Network, attack complexity Low, privileges required None, user interaction None. Impact on confidentiality High, integrity High and availability High.
Which products are affected by CVE-2023-27350?
Public advisories list the following as affected: papercut mf, papercut ng. Check the references on this page for the exact versions each vendor confirms.
How do I fix CVE-2023-27350?
Apply the fix the vendor published — the references on this page link to the primary advisories and patches. When patching can't happen right away, reduce the exposure of the affected component and watch it for exploitation attempts. Rainforest customers see this vulnerability correlated to their own assets and prioritized by real exposure, not by score alone.
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