# CVE-2023-27351: PaperCut NG/MF Improper Authentication

> Remote attackers can bypass authentication in PaperCut NG due to a flaw in the SecurityRequestFilter, allowing unauthorized system access.

- **Severity:** High 8.2 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Yes, since 20 Apr 2026 (CISA KEV), used in ransomware
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Apr 2023
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-2c69-r2jh-xjvm

## What is CVE-2023-27351?

CVE-2023-27351 is a high-severity authentication bypass vulnerability in PaperCut NG, published on 20 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2023-27351?

It affects 2 products.


Products: Papercut Papercut Mf, Papercut Papercut Ng.

## How do I fix CVE-2023-27351?

No fix has been published for CVE-2023-27351 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 4 May 2026.

## Is CVE-2023-27351 being exploited?

Yes. Attackers have exploited CVE-2023-27351 in the wild since at least 20 Apr 2026, including in ransomware campaigns.

Public exploit code:

- PaperCut NG - Authentication Bypass (nuclei): http/cves/2023/CVE-2023-27351.yaml

## Other vulnerabilities in PaperCut NG

- [CVE-2023-27350](https://insights.sbomify.com/CVE-2023-27350/): PaperCut MF/NG Improper Access Control (critical 9.8, exploited in the wild)
- [CVE-2026-82078](https://insights.sbomify.com/CVE-2026-82078/): PaperCut NG/MF Unsafe Reflection (critical 9.4, exploited in the wild)
- [CVE-2026-81578](https://insights.sbomify.com/CVE-2026-81578/): PaperCut NG/MF Missing Authentication for Critical Function (high 8.8, exploited in the wild)
- [CVE-2023-2533](https://insights.sbomify.com/CVE-2023-2533/): PaperCut NG/MF Cross-Site Request Forgery (CSRF) (high 8.4, exploited in the wild)
- [CVE-2023-39143](https://insights.sbomify.com/CVE-2023-39143/): Path traversal in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-27351 and fix it if it is affected.

What it is: CVE-2023-27351 is a high-severity authentication bypass vulnerability in PaperCut NG, published on 20 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2023-27351 in the wild since at least 20 Apr 2026, including in ransomware campaigns.

Affected product: PaperCut NG. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-27351/ (Markdown: https://insights.sbomify.com/CVE-2023-27351/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-27351
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-27351
- OSV: https://osv.dev/vulnerability/CVE-2023-27351

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-27351/
Summaries are generated and may contain mistakes; the official description above is the record.