Threats / PaperCut / CVE-2023-27351
CVE-2023-27351
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-02
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 · 2026-04-205Ransomware use Flagged5EPSS 0.78052 (verify live)6CVSS 8.23CISA SSVC Exploitation: active · Automatable: yes · Impact: total4Exploit Public PoC / detection · nuclei template13
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
87 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-20), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.78052 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 8.2 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N) · Affected: PaperCut, NG/MF. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.0, set at disclosure.
Weakness (CWE)
Mapped to CWE-287 Improper Authentication — weakness family: Authentication.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 1096 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established 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 board1
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’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by zdiCNA
Credited with finding itPiotr Bazydlo (@chudypb) of Trend Micro Zero Day Initiativeunspecified
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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