# CVE-2019-9845: MadsKristensen.AspNetCore.Miniblog subject to Improper Input Validation

> Remote attackers can execute arbitrary ASPX code by uploading malicious files via the blog controller's file saving mechanism.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Apr 2019
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-958r-g534-ccmr

## What is CVE-2019-9845?

CVE-2019-9845 is a critical vulnerability in n/a, published on 16 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

madskristensen Miniblog.Core through 2019-01-16 allows remote attackers to execute arbitrary ASPX code via an IMG element with a data: URL, because SaveFilesToDisk in Controllers/BlogController.cs writes a decoded base64 string to a file without validating the extension.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-9845?

2 open source packages ship an affected version, including MadsKristensen.AspNetCore.Miniblog. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `MadsKristensen.AspNetCore.Miniblog` | NuGet | All versions to 1.0.3 | None |
| `MadsKristensen.AspNetCore.Miniblog` | NuGet | All versions to 1.0.3 | None |

Products: Miniblog.core Project Miniblog.core.

## How do I fix CVE-2019-9845?

No fix has been published for CVE-2019-9845 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-9845 being exploited?

There is no known exploitation of CVE-2019-9845 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2022-37679](https://insights.sbomify.com/CVE-2022-37679/): Cross-site scripting in n/a (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-9845 and fix it if it is affected.

What it is: CVE-2019-9845 is a critical vulnerability in n/a, published on 16 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2019-9845 in the wild and no public exploit code.

Affected packages and fixed versions:
- MadsKristensen.AspNetCore.Miniblog (NuGet): affected all versions up to 1.0.3; no fix listed
- MadsKristensen.AspNetCore.Miniblog (NuGet): affected all versions up to 1.0.3; no fix listed

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-2019-9845/ (Markdown: https://insights.sbomify.com/CVE-2019-9845/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-9845
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-9845
- OSV: https://osv.dev/vulnerability/CVE-2019-9845

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-9845/
Summaries are generated and may contain mistakes; the official description above is the record.