PaperCut NG MF: 2 flaws used in attacks; attackers can get in without a password
OFFICIAL NAMES: PaperCut NG/MF Unsafe Reflection Vulnerability · PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
WHAT IT IS · BUSINESS SOFTWAREIt runs day-to-day business work such as finance, printing, phones or manufacturing.
DO THIS FIRSTAsk the vendor or the team that owns it whether the fix is in. Not sure if you use it? Send this page to your IT provider or security lead and ask.
TECHNICAL SUMMARY 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.
WHY THIS VERDICT Attacks are confirmed. The vulnerability is 63 days old, so current versions are being attacked. Ready-made attack tools are public. The severity score is critical (9.4). The exploit prediction score is 85%.
- HIGHEST CONFIRMED RUNG
- EXPLOITED
- CISA KEV
- LISTED
- EXPLOIT CODE
- READY TO USE
How far has it climbed?
01 TALK
▨ REPORTED, NOT CONFIRMEDNEWEST EVIDENCE · 1 SOURCECVE-2026-82078 discussed publicly (CIRCL sighting).
02 EXPOSED
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETWe have no source that counts exposed systems yet. Internet scan data needs a partnership we do not have. No evidence here does not mean nothing is exposed.
03 TRIED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESAttacks that worked are confirmed (step 4), so attempts count as confirmed too.
- SRC: CISA Known Exploited Vulnerabilities: PaperCut NG/MF Unsafe Reflection Vulnerability · AUG 30
- SRC: CISA Known Exploited Vulnerabilities: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability · AUG 30
- SRC: CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-82078 as actively exploited · AUG 28
- SRC: CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-81578 as actively exploited · AUG 28
04 EXPLOITED
■ CONFIRMEDNEWEST EVIDENCE · 2 INDEPENDENT SOURCESPaperCut NG/MF contains an unsafe reflection vulnerability that allows an attacker to manipulate system configuration parameters and execute arbitrary Java bytecode residing on the application classpath under the security context of the PaperCut server process. This vulnerability can be chained with CVE-2026-81578. 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.
- SRC: CISA Known Exploited Vulnerabilities: PaperCut NG/MF Unsafe Reflection Vulnerability · AUG 30
- SRC: CISA Known Exploited Vulnerabilities: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability · AUG 30
- SRC: CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-82078 as actively exploited · AUG 28
- SRC: CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-81578 as actively exploited · AUG 28
05 DAMAGE
□ NOT TRACKED YETNO SOURCE FOR THIS STEP YETBreach notices and filings rarely name the flaw that was used, so we cannot link them to this event yet. No evidence here does not mean no harm.
When each thing happened
- DISCLOSED
- EXPLOIT CODE PUBLICDATE UNKNOWN
- FIRST ATTACK REPORT
- CISA KEV LISTING
- US FEDERAL DEADLINE
THE FIX
CISA's instruction: apply the vendor's fix, or stop using the product if no fix exists. The deadline CISA set for US federal agencies, Sep 14, 2026, has passed. It is a US government deadline; use it as a guide.
Questions to ask this week
- Do we run PaperCut NG MF? If yes, is it patched or cut off from the internet?
- Who owns fixing it, and by what date?
- Have we checked for signs of attack since the first report, not just since the patch?
How it unfolded
- AUG 26, 2026Metasploit exploit module: PaperCut NG/MF Unauthenticated RCE (CVE-2026-81578 + CVE-2026-82078)
- Attack activity. AUG 28, 2026CISA Vulnrichment marks CVE-2026-81578 as actively exploited
- Attack activity. AUG 28, 2026CISA Vulnrichment marks CVE-2026-82078 as actively exploited
- AUG 29, 20262 public GitHub repositories claim a proof of concept for CVE-2026-81578
- Attack activity. AUG 30, 2026PaperCut NG/MF Unsafe Reflection Vulnerability
- Attack activity. AUG 30, 2026PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
- OCT 27, 2026CVE-2026-82078 discussed publicly (CIRCL sighting)
SOURCES
- [1] nuclei-templates: Nuclei scan template: PaperCut NG/MF <=26.0.4 - Unauthenticated ConfigEditor Access via Tapestry Complex-Direct, OCT 24
- [2] CIRCL Vulnerability-Lookup sightings: CVE-2026-82078 discussed publicly (CIRCL sighting), OCT 27
- [3] CISA Known Exploited Vulnerabilities: PaperCut NG/MF Unsafe Reflection Vulnerability, AUG 30
- [4] CISA Known Exploited Vulnerabilities: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability, AUG 30
- [5] PoC-in-GitHub: 2 public GitHub repositories claim a proof of concept for CVE-2026-81578, AUG 29
- [6] CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-82078 as actively exploited, AUG 28
- [7] CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2026-81578 as actively exploited, AUG 28
- [8] Metasploit module metadata: Metasploit exploit module: PaperCut NG/MF Unauthenticated RCE (CVE-2026-81578 + CVE-2026-82078), AUG 26