CVE-2023-27351: PaperCut NG/MF Improper Authentication Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 20 Apr 2026, 1,096 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 78.1%
EPSS score, percentile 99.6 of all scored records
- How severe?
- 8.2 High
CVSS v3.0 base score, given by the CNA
- What should I do?
CISA deadline 4 May 2026. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- 22.0.5 (Build 63914)
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: 4 May 2026.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 22.0.5 (Build 63914) |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2023-27351 to its Known Exploited Vulnerabilities (KEV) catalog on 20 Apr 2026.
- CISA marks it as known to be used in ransomware campaigns.
- The due date CISA sets for the required action is 4 May 2026.
- The CVE record was published on 20 Apr 2023, 1,096 days before it was added to KEV.
- The CVE record carries a CVSS v3.0 base score of 8.2 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 78.1% (percentile 99.6), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-287: Improper Authentication
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 20 Apr 2023 | CVE record published |
| 20 Apr 2026 | Added to CISA KEV |
| 4 May 2026 | CISA due date for the required action |
| 1 Oct 2026 | CVE record last updated |
References
More exploited PaperCut vulnerabilities
- CVE-2026-81578: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
- CVE-2026-82078: PaperCut NG/MF Unsafe Reflection Vulnerability
- CVE-2023-2533: PaperCut NG/MF Cross-Site Request Forgery (CSRF) Vulnerability
- CVE-2023-27350: PaperCut MF/NG Improper Access Control Vulnerability