# CVE-2023-27351: NG - Authentication Bypass

> Live exploitation tracking for CVE-2023-27351 by the CrowdSec Live Exploit Tracker, built from real-world attack data crowdsourced from CrowdSec's global network.

Page: https://tracker.crowdsec.net/cves/CVE-2023-27351

## Key facts

- **Exploitation phase:** Limited Exploitation. The vulnerability is known but shows very limited attacker interest or exploitation activity.
- **CVSS score:** 7.5
- **Public exploit available:** Yes
- **Affected products:** PaperCut NG
- **Weaknesses:** CWE-287 (Improper Authentication)
- **Tags:** management_panel, enterprise_software

## Description

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.

## CrowdSec analysis

[CVE-2023-27351](https://euvd.enisa.europa.eu/vulnerability/CVE-2023-27351) is an authentication bypass vulnerability in PaperCut NG 22.0.5, allowing remote attackers to gain unauthorized access to the system without valid credentials. Exploiting a flaw in the SecurityRequestFilter class, attackers can circumvent authentication mechanisms, potentially exposing sensitive information and administrative functions to unauthorized users.

CrowdSec has been tracking this vulnerability and its exploits since 14th of January 2026.

Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2023-27351 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning.
CrowdSec data also reveals a clear uptick in attacks involving CVE-2023-27351 over the past week. Activity is above the usual baseline, suggesting growing attention from attackers. This may reflect rising awareness, recent exploit releases, or expanded targeting efforts.

Attackers exploit this vulnerability by sending crafted POST requests to endpoints such as `/rpc/api/rest/master/user/createInternalUser;/keepalive` and `/rpc/api/rest/master/user/getExportedUser;/keepalive`, bypassing authentication controls to create and access internal user accounts.

## Timeline

- 2023-04-20: CVE Published. CVE-2023-27351 is published to NVD.
- 2026-01-14: Rule Released. CrowdSec releases a rule to detect CVE-2023-27351 exploitation attempts against the CrowdSec Network.
- 2026-01-19: CrowdSec First Seen. CrowdSec observes in-the-wild exploitation of CVE-2023-27351 for the first time.
- 2026-04-20: CISA KEV. CVE-2023-27351 is added to the Known Exploited Vulnerabilities catalog by CISA.
- 2026-05-04: CISA Remediation Deadline. Expiration of the CISA remediation deadline as described in [BOD 22-01](https://www.cisa.gov/news-events/directives/bod-22-01-reducing-significant-risk-known-exploited-vulnerabilities).

## References

- https://www.zerodayinitiative.com/advisories/ZDI-23-232/
- https://www.papercut.com/kb/Main/PO-1216-and-PO-1219
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-27351.yaml

## Live exploitation data

The [Live Exploit Tracker page](https://tracker.crowdsec.net/cves/CVE-2023-27351) follows observed exploitation activity for CVE-2023-27351. [Request an API key](https://tracker.crowdsec.net/request-api-key) for full access to its exploitation timeline, attacking IP addresses and blocklists.