CVE-2026-81578

PaperCut NG/MF authentication bypass, confirmed exploited in the wild.

PaperCut NG/MF contains a missing authentication for critical function vulnerability which allows an unauthenticated remote attacker to modify certain system configurations. This vulnerability can be chained with CVE-2026-82078.

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85%chance of exploitation in the next 30 days (EPSS), 99th percentile

31 Augadded to CISA's Known Exploited Vulnerabilities list, 2026

14 Sepfederal remediation deadline, already passed

Passedpast the deadline: patch now

CISA's name for it	PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
Vendor and product	PaperCut · NG/MF
Type	authentication bypass · CWE-306
Exploited	Confirmed by CISA listed 31 August 2026
Likelihood	one of the most likely to be exploited of every vulnerability tracked
Deadline	14 September 2026 · already passed
Used in ransomware	Not reported
Advisories	www.papercut.com ↗ · www.cisa.gov ↗ · www.cisa.gov ↗ · nvd.nist.gov ↗

What to do

Three steps, in this order

Step 1

Apply the vendor fix and restart the affected service.

Step 2

Put the login or management interface behind a VPN or allow-list; a bypass makes passwords irrelevant.

Step 3

Rotate credentials and session keys the product holds, and review accounts and configuration changes since the listing date.

CISA's required action	Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

CISA's required action

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

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Questions

CVE-2026-81578 in short

Is CVE-2026-81578 being exploited?

Yes. CISA added CVE-2026-81578 to its Known Exploited Vulnerabilities catalogue on 31 August 2026, which it does only on evidence of exploitation in the wild.

What is the CISA deadline for CVE-2026-81578?

US federal agencies must remediate it by 14 September 2026. Everyone else should treat that date as the latest safe point to patch an internet-facing system.

How likely is CVE-2026-81578 to be exploited in the next 30 days?

FIRST's Exploit Prediction Scoring System gives it 85%, the 99th percentile of every CVE it scores.

How do I fix CVE-2026-81578?

Apply the vendor fix and restart the affected service. Put the login or management interface behind a VPN or allow-list; a bypass makes passwords irrelevant. Rotate credentials and session keys the product holds, and review accounts and configuration changes since the listing date.

Same vendor

Other PaperCut vulnerabilities being exploited

CVE	Product	Type	Listed
CVE-2026-82078	NG/MF	exploited vulnerability	31 August 2026
CVE-2023-27351	NG/MF	authentication bypass	20 April 2026

Sources: CISA Known Exploited Vulnerabilities catalogue (released 10 November 2026) and FIRST EPSS. Page compiled automatically by SAK T.L.M, the threat-intelligence tool of SAK T.E.C, on 13 November 2026.