Exploited CVEs / CVE-2023-27351

CVE-2023-27351

PaperCut NG/MF Improper Authentication Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2026-05-04 (that deadline has passed); treat that date as the outer bound for your own environment. Check the vendor security advisory for the fix.

Risk summary

HighCISA KEVRansomware

7.5

CVSS v3 base

78%

EPSS exploit probability

High

Severity

2026-04-20

Added to KEV

2026-05-04 (past due)

CISA due date

Actively exploited PaperCut NG/MF vulnerability, High severity, CVSS v3 7.5. Added to the CISA KEV catalog 2026-04-20.

Senserva AI read on CVE-2023-27351 CISA required action Official fix for CVE-2023-27351 Admin questions #30 hottest CVE right now

Senserva AI Opinion for CVE-2023-27351

This is an authentication bypass in PaperCut NG/MF that lets remote attackers slip past login through the SecurityRequestFilter class, no credentials needed. Anyone running an internet-reachable PaperCut print management server is exposed, and with a 77 percent EPSS score plus confirmed ransomware use and CISA KEV listing, this is a proven entry point rather than a theoretical risk.

Do this: Patch every PaperCut NG/MF server to a fixed release now, and restrict the admin and web interfaces from public internet access until you confirm the update is applied.

AI-generated from public data, 2026-07-22. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2023-27351

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2023-27351, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2023-27351.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2023-27351: PaperCut NG/MF Improper Authentication Vulnerability
- Affected: PaperCut NG/MF
- Severity: High, CVSS v3 7.5; EPSS 30-day exploitation probability 78%
- Added to CISA KEV: 2026-04-20; federal remediation due 2026-05-04
- Ransomware-linked: YES
- CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

No vendor fix is mapped yet. This page refreshes daily and will name the patch the day one is published.

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated August 29, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2023-27351

Published: 2026-04-20
Last revised: 2026-04-20
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.

2026-04-20 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 7.5; EPSS first scored at 77.4%
2026-08-29 EPSS 77.4% to 78.0%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2026-05-04 (past due).

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Official fix for CVE-2023-27351

Check the vendor's security advisory channel for the patched NG/MF versions and workarounds.

CISA KEV entry

Common questions about CVE-2023-27351

Is CVE-2023-27351 actively exploited?

Yes. CVE-2023-27351 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2026-04-20, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 78%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2023-27351?

CISA set the federal (BOD 22-01) remediation due date at 2026-05-04, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

What fixes CVE-2023-27351?

Check the vendor's security advisory for the patched NG/MF versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2023-27351?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2023-27351's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited PaperCut CVEs: CVE-2023-2533 CVE-2023-27350
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.