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Threats / PaperCut / CVE-2023-27351
CVE-2023-27351 · EUVD no mirror located · GCVE no mirror located Verified 2026-06-07

PaperCut NG/MF vulnerability

PaperCut NG/MF contains an improper authentication vulnerability in the SecurityRequestFilter class that allows remote attackers to bypass authentication controls.

Verdict

Today item, not a backlog item.

This authentication bypass vulnerability has been actively exploited in the wild and leveraged in ransomware campaigns. The high EPSS score reflects significant exploitation risk. Organizations running affected versions face immediate compromise risk.

CISA KEV Yes · 2026-04-203Ransomware use Flagged3EPSS 0.83284 (verify live)4
01

Is it exploitable?

— the evidence, ranked above the score
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-20), flagged for known ransomware use.
CISA KEV ↗Confirmed
Probability (EPSS)
EPSS 0.83284 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
FIRST EPSS ↗High
Severity / affected
Affected: PaperCut, NG/MF. Confirm exact fixed builds in the vendor advisory.
NVD ↗Reported
Weakness (CWE)
Mapped to CWE-287 Improper Authentication — weakness family: Authentication.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
NVD ↗Reported
WeaknessCWE-287 · Improper AuthenticationAuthentication
02

Who’s exploiting it?

— attribution turns risk into urgency
Attribution not established

No threat-actor attribution is established from the public feed for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.

03

Why it matters

— the attack path, told twice: adversary, then board
1

Front door — unauthenticated access narrative 1

Attacker
I craft a request that bypasses the SecurityRequestFilter authentication mechanism to gain unauthorized access to the PaperCut instance.
Business
Attackers obtain unauthenticated access to print management systems, enabling lateral movement and data exfiltration.
2

Keys to the kingdom — privilege/identity takeover narrative 2

Attacker
I establish persistence and escalate privileges within the compromised PaperCut environment to deploy ransomware payloads.
Business
Ransomware operators encrypt critical print infrastructure and business systems, disrupting operations and demanding payment.
3

Lateral reach — past segmentation narrative 3

Attacker
I exfiltrate sensitive documents and credentials stored within or accessible through the print management system.
Business
Confidential business data, financial records, and employee information are stolen and potentially sold or published.
04

What to do

— defensible action
  • Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05

Coverage & confidence

— what we know, and what we don’t

Established (cited)

  • KEV listing (CISA)
  • Ransomware-use flag (CISA)
  • EPSS probability (FIRST)
  • CWE weakness mapping (NVD)
  • Catalogued by zdi (CNA)
  • Named finder/reporter credit (CVE.org)

    • Coverage gaps — stated, not hidden

  • No EUVD / GCVE mirror in feed — single-authority dependency for the identifier.
  • EPSS & exposure are time-varying; verify live at the source.
  • Threat-actor attribution not established from feed data — absence of a name is not absence of compromise.
    • Disclosure & credit2
    Catalogued by zdiCNA
    Credited with finding itPiotr Bazydlo (@chudypb) of Trend Micro Zero Day Initiativeunspecified