# CVE-2021-20873: Missing authorization in Yappli

> Attackers can redirect users to unintended sites via crafted URLs due to improper authorization in the Custom URL Scheme handler of Yappli-based Android apps.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 28 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-qqj9-5rm5-5hhr

## What is CVE-2021-20873?

CVE-2021-20873 is a high-severity missing authorization vulnerability in Yappli, Inc. Yappli, published on 28 Dec 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Yappli is an application development platform which provides the function to access a requested URL using Custom URL Scheme. When Android apps are developed with Yappli versions since v7.3.6 and prior to v9.30.0, they are vulnerable to improper authorization in Custom URL Scheme handler, and may be directed to unintended sites via a specially crafted URL.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2021-20873?

It affects 1 product.


Products: Yappli Yappli.

## How do I fix CVE-2021-20873?

No fix has been published for CVE-2021-20873 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20873 being exploited?

There is no known exploitation of CVE-2021-20873 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20873 and fix it if it is affected.

What it is: CVE-2021-20873 is a high-severity missing authorization vulnerability in Yappli, Inc. Yappli, published on 28 Dec 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-20873 in the wild and no public exploit code.

Affected product: Yappli, Inc. Yappli. 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-2021-20873/ (Markdown: https://insights.sbomify.com/CVE-2021-20873/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20873
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20873
- OSV: https://osv.dev/vulnerability/CVE-2021-20873

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20873/
Summaries are generated and may contain mistakes; the official description above is the record.