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PaperCut NG/MF Missing Authentication for Critical Function Vulnerability

Exploited · KEV 2026-08-31Metasploit moduleCVE-2026-81578CWE-305

Exploited since 2026-08-31. 1 of 8 rule sources name it. Our CRS test: partly blocked.

Edge rules
1/8
Our test
Partly blocked
CVSS
8.8
EPSS
84.7% Top 0.3%
Posts, 14d
02026-10-20: 0 posts2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts
Published
2026-08-28
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… More

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.

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AI · answers from this page
Ask about CVE-2026-81578: who's covered, what to patch first, how vendors compare. I cite sources and won't help with attacks.

Workers AI (Llama 3.3). Can be wrong: check the cited source.

Severity, decoded

CVSS 4.0
High · 8.8 / 10

Exploitable over the network, with no privileges and no user interaction, leading to low impact on confidentiality and availability and full loss of integrity.

Over the internetNo login neededNo user actionWorks reliablySerious impact
How the score is built11 metrics
  • Attack vectorAn attacker can reach it over the internet; no access to your network needed.
    Network
  • Attack complexityNo built-in defences have to be bypassed; the attack works reliably.
    Low
  • Attack requirementsThe attack works without any special deployment or timing conditions.
    None
  • Privileges requiredNo account or login is needed.
    None
  • User interactionNo one has to click or open anything; the attack works on its own.
    None
  • Confidentiality impact (vulnerable system)An attacker can read some data, but has no control over what they get.
    Low
  • Integrity impact (vulnerable system)An attacker can change any data or files the affected component protects.
    High
  • Availability impact (vulnerable system)An attacker can slow the component down or interrupt it now and then.
    Low
  • Confidentiality impact (other systems)Other systems' data is not exposed.
    None
  • Integrity impact (other systems)Other systems' data cannot be changed.
    None
  • Availability impact (other systems)Other systems keep working normally.
    None
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
CISA's assessmentSSVC, from the CVE record
ExploitationActive

Attackers are exploiting this in the wild.

AutomatableYes

Attackers can script the attack end to end and hit many targets at once.

Technical impactPartial

A successful attack gives limited control over the affected software or limited access to its data.

Public exploits

2 found
1 Metasploit0 Exploit-DB1 Scanner template0 GitHub PoCs

Links are to third-party code: never run it outside an isolated lab.

Timeline

  1. 2026-08-27
    Metasploit module published
    PaperCut NG/MF Unauthenticated RCE (CVE-2026-81578 + CVE-2026-82078)
  2. 2026-08-28
    CVE published
    CVE List
  3. 2026-08-31
    Added to CISA KEV
    Confirmed exploitation in the wild
  4. 2026-10-21
    F5 rule names it
    Earliest entry we can see is an update
  5. 2026-11-02
    Our test: OWASP Core Rule Set blocked part of it
    paranoia level 1, anomaly threshold 5, default CRS settings
  6. 2026-11-02
    Our test: OWASP Core Rule Set blocked part of it
    paranoia level 2, anomaly threshold 5, default CRS settings

Social

2026-10-20: 0 posts2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts

No posts seen yet on X, Bluesky, Mastodon, Hacker News or GitHub.

Vendor statements

Quoted
CloudflareWAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Each row gives the rule ID and its default action. The feed starts in January 2025, so older rules are missing.

AWSAWS WAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. AWS often describes a vulnerability without naming its CVE (for example "Log4j"). We count only entries that name the CVE, so AWS coverage is understated.

Microsoft AzureFront Door and Application Gateway WAF (DRS)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. The rule tables name CVEs but carry no dates, so Azure is left out of every time-to-rule figure.

Google CloudCloud Armor preconfigured WAF rulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Google names few CVEs: the release notes start in May 2024 and the rules reference lists CVEs without dates. Its cve-canary rules are opt-in.

FastlyNext-Gen WAF virtual patchesBefore feed history

The CVE predates the oldest entry in this vendor's public feed, so a rule may exist that we cannot see.

F5Attack signatures (Distributed Cloud WAF)1 quoteRule published

Named by 2026-10-21; the first entry is an update, so the rule may be older.

2026-10-21Updated200013222Source
Updated: signature 200013222 "PaperCut NG/MF Authentication Bypass" (Authentication/Authorization Attacks, risk High), systems: Other Web Server. References: CVE-2026-81578, CVE-2026-82078.
AkamaiApp & API Protector (Adaptive Security Engine)No public source

This vendor publishes no machine-readable rule changelog we can check.

OWASP CRSCore Rule Set (open source, used inside many WAFs)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. CRS rarely names CVEs: it relies on generic detections. Our own lab measures what it actually blocks.