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Exploited vulnerability · CISA KEV

Is CVE-2023-27351 exploited? Yes: in CISA KEV since 20 Apr 2026

Gociux · PaperCut NG/MF · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2023-27351, PaperCut NG/MF Improper Authentication Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 20 Apr 2026, 1096 days after it was published. It is known to be used in ransomware campaigns. It affects PaperCut NG/MF. If you run it, CISA's required action is: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

exploitedYesCISA KEV · 20 Apr 2026
ransomwareKnownused in campaigns
EPSStop 1%among the most likely CVEs to be exploited
severity8.2CVSS 3.0 · high
US federal due4 May 2026BOD 22-01 deadline

What it is

PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class.

VendorPaperCut (5 exploited CVEs in KEV)
ProductNG/MF
VulnerabilityPaperCut NG/MF Improper Authentication Vulnerability
WeaknessCWE-287
Published20 Apr 2023
Added to KEV20 Apr 2026
Reported by (CNA)zdi

What to do

  1. Check whether you run it. Look for NG/MF in your asset inventory, including appliances and cloud images. Stack check lists every exploited PaperCut CVE at once.
  2. Apply the fix. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 20 Apr 2023.
  4. Get told next time. Email alerts when CISA adds a CVE for PaperCut.

Other exploited CVEs in NG/MF

References

Questions

Is CVE-2023-27351 being exploited?

Yes. CISA added CVE-2023-27351 to the Known Exploited Vulnerabilities catalog on 20 Apr 2026, which means there is reliable evidence of exploitation in the wild.

Is CVE-2023-27351 used in ransomware attacks?

Yes, CISA lists it as known to be used in ransomware campaigns.

How do I fix CVE-2023-27351?

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Check PaperCut's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected NG/MF and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in April 2026 · PaperCut scorecard · act-now radar.

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