This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914).
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.
- Published
- Apr 20, 2023
- Updated
- Jun 17, 2026
- EPSS
- 78.1% · 100th percentile
- CWE
- CWE-287
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Report tools
Action score
83
Now
Patch today or shut off access.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 30 / 30 · Listed
- EPSS
- 23 / 30 · 78.1%
CISA SSVC decision
- Exploitation
- active
- Automatable
- yes
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 7.5
- CNA · zdi
- 8.2
- 0.7 point gap
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Actively exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on Apr 20, 2026. That signals real attacks, not theory.
Remediation deadline for government agencies: May 4, 2026.
Known to be used in ransomware campaigns.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| papercut | papercut mf | cpe:2.3:a:papercut:papercut_mf |
| papercut | papercut ng | cpe:2.3:a:papercut:papercut_ng |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- papercut papercut mf15.0 and later · before 20.1.7
- papercut papercut mf21.0.0 and later · before 21.2.11
- papercut papercut mf22.0.0 and later · before 22.0.9
- papercut papercut ng15.0 and later · before 20.1.7
- papercut papercut ng21.0.0 and later · before 21.2.11
- papercut papercut ng22.0.0 and later · before 22.0.9
Versions reported by the vendor
Affected version ranges reported by the assigning authority (zdi). Independent of NVD's CPE analysis and usually ahead of it.
PaperCut NG
- 22.0.5 (Build 63914)affected
Same product
papercut: all recordsOther highest-scoring records for the same primary product.
- CVE-2023-27350This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914).KEV99Now
- CVE-2023-2533PaperCut MF/NG 22.0.10 (Build 65996 2023-03-27) - Remote code execution via CSRFKEV74This week
- CVE-2026-82078PaperCut MF/NG: Unsafe Dynamic Class Loading in Database ConnectorKEV68This week
- CVE-2026-81578PaperCut MF/NG: Authentication BypassKEV66This week
- CVE-2023-39143PaperCut NG and PaperCut MF before 22.1.3 on Windows allow path traversal, enabling attackers to upload, read, or delete arbitrary files.63This week
- CVE-2024-1222Incorrect authorization controls in PaperCut NG/MF APIs58Plan
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
Weaponized
A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.
Evidence
- Nuclei detection template ×1
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Nuclei detection template | Nuclei template CVE-2023-27351 | — |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Published
- CISA KEV+1095 d
- TodaySep 29, 2026+1258 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- none
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- None
- Availability impact
- None
Weakness class (CWE)
CWE-287 · Improper AuthenticationCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
nvd-primary
Root cause
Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.
The bug in code
The whole CWE-287 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
app.use("/admin", requireSession, adminRouter);
// Route added later skips the middlewareapp.post("/admin-api/config", updateConfig);Fixed
const admin = express.Router();admin.use(requireSession, requireRole("admin"));
admin.post("/config", updateConfig);app.use("/admin", admin);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Authentication AbuseCAPEC-114Medium
- Authentication BypassCAPEC-115Medium
- Identity SpoofingCAPEC-151likelihood: Medium · Medium
- Fake the Source of DataCAPEC-194Medium
- Exploiting Trust in ClientCAPEC-22likelihood: High · High
- Utilizing REST's Trust in the System Resource to Obtain Sensitive DataCAPEC-57likelihood: Medium · Very High
- Session HijackingCAPEC-593likelihood: High · Very High
- Token ImpersonationCAPEC-633Medium
ATT&CK techniques
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
- www.papercut.com/kb/Main/PO-1216-and-PO-1219
- www.zerodayinitiative.com/advisories/ZDI-23-232/
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27351
Vendor advisories and official records. Exploit/PoC links are deliberately left out.