CASCACascade Atlas

Evidence dossier

CVE-2023-27351

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914).

Exploited in the wild (CISA KEV since Apr 20, 2026). NVD reports CVSS 3.1 7.5. EPSS estimates 77.4% exploit likelihood as of Aug 26, 2026.

79.9–81.2Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

State
PUBLISHED
Published
Apr 20, 2023
Updated
Apr 21, 2026
Evidence coverage
97%

Evidence chronology

What was known when

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  1. Source dateSource date omittedFirst observed by CASCA
    CISA-ADP

    Record text: CISA ADP Vulnrichment

    Inspect raw assertion
    Field
    container
    Value
    CISA ADP Vulnrichment
    Original evidence ↗
  2. Source dateSource date omittedFirst observed by CASCA
    CVE Program

    Record text: CVE Program Container

    Inspect raw assertion
    Field
    container
    Value
    CVE Program Container
    Original evidence ↗
  3. Source dateSource date omittedFirst observed by CASCA
    zdi

    Record text: This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

    Inspect raw assertion
    Field
    container
    Value
    This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: PaperCut NG/MF Improper Authentication Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    PaperCut NG/MF Improper Authentication Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 77.39% probability · 99.52th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.773880000000; percentile 0.995190000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Apr 20, 2026 · first observed Jul 19, 2026

Exploit likelihood77.39%

FIRST EPSS · score date Aug 26, 2026 · 99.5th percentile · first observed Aug 26, 2026

SeverityCVSS 7.5

NVD · CVSS 3.1 · first observed Jul 19, 2026 · same-version scores align in this snapshot

Evidence detail

Source limits and decisions

Why each evidence state has this value

casca-unknown-reasons-v1
Exploitation statusEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Aug 27, 2026
Resolution
None
Exploit likelihoodEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Aug 27, 2026
Resolution
None
Severity assessmentEvidence supported

Eligible evidence is present for this bounded claim.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Aug 27, 2026
Resolution
None
Affected productsSource-reported scope

The cited source assertion is retained while canonical product linkage remains open.

Revision
casca-factor-d-obligations-v1
Cutoff
Aug 27, 2026
Resolution
Resolve identity

Source comparison

Who said what

CISA-ADPIndependent enrichment
Record text

CISA ADP Vulnrichment

Inspect raw assertion
Field
container
Value
CISA ADP Vulnrichment
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CVE ProgramDerivative copy
Record text

CVE Program Container

Inspect raw assertion
Field
container
Value
CVE Program Container
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
zdiOriginal assertion
Record text

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

Inspect raw assertion
Field
container
Value
This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

PaperCut NG/MF Improper Authentication Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
PaperCut NG/MF Improper Authentication Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

77.39% probability · 99.52th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.773880000000; percentile 0.995190000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
6Underlying assertions
2Canonical products
6Target assertions
0Constraint assertions

Grouped from 1 configuration nodes in this exact snapshot. Visual grouping is navigational; asset exposure and root cause require cited evidence.

Identity source boundaries
  • Cpe dictionary1,775,266 records · observed through 2026-07-21T06:45:29.809Z27d65b0f-b718-4b4f-bb79-c47c68d09dfa
  • Cpe match643,502 records · observed through 2026-07-21T08:13:17.697Z955dae73-7302-438b-aee1-058d7cc5d48e

3 scope groups

zdi · source assertedPaperCutNGDirect source scope
Affected: 22.0.5 (Build 63914)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "22.0.5 (Build 63914)"}]
NVD CPE · APPLICATIONpapercutpapercut_mfVulnerable target · 3 assertions
Any version (unconstrained) (>= 15.0, < 20.1.7); Any version (unconstrained) (>= 21.0.0, < 21.2.11); Any version (unconstrained) (>= 22.0.0, < 22.0.9)Canonical identity product-14dcf5eeaf50aac0f976e8addf97fc8443e6dba787dc748af9188d8bb500a783Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:papercut:papercut_mf:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    from including 22.0.0; through excluding 22.0.9
    Match ID
    a326e88d-635e-4ac1-b5ce-455306fc9d55
  2. cpe:2.3:a:papercut:papercut_mf:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    from including 15.0; through excluding 20.1.7
    Match ID
    b754bd95-f7cc-4a77-a5fb-b627e1e636db
  3. cpe:2.3:a:papercut:papercut_mf:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    from including 21.0.0; through excluding 21.2.11
    Match ID
    7d231c34-f58c-4ca1-b158-64778ac17991
NVD CPE · APPLICATIONpapercutpapercut_ngVulnerable target · 3 assertions
Any version (unconstrained) (>= 15.0, < 20.1.7); Any version (unconstrained) (>= 21.0.0, < 21.2.11); Any version (unconstrained) (>= 22.0.0, < 22.0.9)Canonical identity product-bacdf95818ebe4d4b7864029d8b2827411ae884ae2fe2e1bb3cf52ca7e265fb3Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:papercut:papercut_ng:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 4
    Logic
    OR
    Version bounds
    from including 21.0.0; through excluding 21.2.11
    Match ID
    4de19845-02f0-4bb9-becb-49b34facb55d
  2. cpe:2.3:a:papercut:papercut_ng:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 3
    Logic
    OR
    Version bounds
    from including 15.0; through excluding 20.1.7
    Match ID
    bfb91de7-faea-4f7d-b4b6-6b5211de4ad0
  3. cpe:2.3:a:papercut:papercut_ng:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 5
    Logic
    OR
    Version bounds
    from including 22.0.0; through excluding 22.0.9
    Match ID
    c1852e7b-0b3f-4208-a26e-cb117e0c0cd8

Affected-product evidence

Accepted scope and product mapping

2 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-2022050333d91159667dee48255d2bd9f768d58f2e5cde816a1fcb844338627d · product-14dcf5eeaf50aac0f976e8addf97fc8443e6dba787dc748af9188d8bb500a783

Source class
Nvd cpe vulnerable target
Assertions
3
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
58ff118c-b55b-42a2-aa7a-44ffa2afba3f8fe768d7-5bc1-41a9-8260-4e8f51f225689a676f46-7baa-4224-8aae-0a5b6350a6a5
Mapping establishedEvidence supported

vendor-2022050333d91159667dee48255d2bd9f768d58f2e5cde816a1fcb844338627d · product-bacdf95818ebe4d4b7864029d8b2827411ae884ae2fe2e1bb3cf52ca7e265fb3

Source class
Nvd cpe vulnerable target
Assertions
3
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
462cf79c-8ac4-40c4-a802-0d9b643f283ab586d87a-4e01-412b-beac-10cfc9b41ec8c307c838-61cb-4a9d-b31a-dd62719ccd7f
Source-reported scopeSource-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Vendor specified only by source · Product specified only by source

Source class
Direct cve affected
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
20073116-74e6-485b-9a20-5c3d30803c00

Assessments

CVSS by origin

7.5
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
8.2
zdi-disclosures@trendmicro.comCVSS 3.0 · role Secondary · priority eligiblevalid_matchCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
8.2
zdiCVSS 3.0 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Direct CVE/CNA normalized decisions

8.2Priority eligible

zdi

CVSS 3.0 · Primary · Original assertion · rank 1

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
Validation
Valid match
Recomputed
8.2
Decision reason
Evidence supported
Policy
casca-direct-cvss-eligibility-v1

Assessments are retained side by side under closed precedence. Cascade never averages CVSS.

Evidence boundaries

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; remaining scope stays source-scoped.
  • NVD-carried upstream facts remain derivative; independent corroboration requires a separately authored source.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.
  • OSV aggregation and OSV-converted NVD material are not independent corroboration.
  • Red Hat facts are vendor assertions for the exact supplied products.
  • Nonmembership and not-yet-observed states are not proof of safety.