CVE-2026-81578
CVE-2026-81578 is a security flaw in PaperCut NG/MF, printing software offices and schools use. Attackers can get into PaperCut NG/MF without a valid password. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 31 Aug 2026.[1]
PaperCut NG/MF is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 24.1.10, 25.0.13 and 26.0.5 of PaperCut MF/NG.
Description
CISA calls it a missing authentication for critical function in PaperCut NG/MF. In its words: “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.”[1]
The CVE record adds: “An improper access control vulnerability exists in the web management interface of PaperCut MF and PaperCut NG. Under specific conditions, unauthenticated remote requests targeting administrative functions can trigger backend actions prior to the completion of access validation checks. This allows an unauthenticated remote attacker to modify certain system configurations.”[2]
The underlying weakness is missing authentication (CWE-306), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| PaperCut MF/NG | 24.1.10 |
| PaperCut MF/NG | 25.0.13 |
| PaperCut MF/NG | 26.0.5 |
Most families won’t have PaperCut NG/MF; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 31 Aug 2026, 3 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 14 Sep 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 85%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
PaperCut has published a fix or advice.[3] 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).”[1]
- Check whether you use it.PaperCut NG/MF is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 24.1.10, 25.0.13 and 26.0.5 of PaperCut MF/NG), or not in use. CISA gave US government agencies until 14 Sep 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 85%.[4] |
See also
Other PaperCut NG/MF flaws
- CVE-2026-82078: unsafe reflection ·
- CVE-2023-27351: improper authentication ·
- CVE-2023-2533: cross-site request forgery (CSRF) ·
Other PaperCut flaws
- CVE-2023-27350, PaperCut MF/NG: improper access control ·
Other missing authentication flaws
- CVE-2026-111357, Ivanti Connect Secure: missing authentication for critical function ·
- CVE-2026-67277, MikroTik RouterOS: missing authentication for critical function ·
- CVE-2026-72529, TrueConf Server: missing authentication for critical function ·
- CVE-2026-56164, Microsoft SharePoint Server: missing authentication for critical function ·
- CVE-2026-20253, Splunk Enterprise: missing authentication for critical function ·
Added the same day
- CVE-2026-82078, PaperCut NG/MF: unsafe reflection ·
Every PaperCut flaw on CISA’s list · Everything added in August 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “PaperCut NG/MF Missing Authentication for Critical Function Vulnerability”. Known Exploited Vulnerabilities Catalog, added 31 Aug 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-81578 Detail”. National Vulnerability Database, published 28 Aug 2026.
- ^ PaperCut. Advisories and fixes: papercut.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.847, percentile 99.7, 31 Oct 2026.
- CVE Program. “CVE-2026-81578”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.