# OSV-2021-563: Heap-use-after-free in AK::NonnullOwnPtr<JS::IndexedPropertyStorage>::operator->

> A heap-use-after-free vulnerability in the SerenityOS browser's JavaScript engine allows attackers to execute arbitrary code or cause a denial of service via crafted web content.

- **Severity:** Not scored
- **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:** 26 Mar 2021

## What is OSV-2021-563?

OSV-2021-563 is an use after free vulnerability in serenity, published on 26 Mar 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

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=32459

```
Crash type: Heap-use-after-free READ 8
Crash state:
AK::NonnullOwnPtr<JS::IndexedPropertyStorage>::operator->
JS::IndexedProperties::array_like_size
JS::IndexedProperties::append
```

## Which versions are affected by OSV-2021-563?

1 open source package ship an affected version, including serenity.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `serenity` | OSS-Fuzz | All versions | None |

## How do I fix OSV-2021-563?

No fix has been published for OSV-2021-563 yet. Limit exposure of the affected software until one is available.

## Is OSV-2021-563 being exploited?

There is no known exploitation of OSV-2021-563 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for OSV-2021-563 and fix it if it is affected.

What it is: OSV-2021-563 is an use after free vulnerability in serenity, published on 26 Mar 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 OSV-2021-563 in the wild and no public exploit code.

Affected packages and fixed versions:
- serenity (OSS-Fuzz): affected all versions; 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/OSV-2021-563/ (Markdown: https://insights.sbomify.com/OSV-2021-563/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/OSV-2021-563

---
From sbomify Insights: https://insights.sbomify.com/OSV-2021-563/
Summaries are generated and may contain mistakes; the official description above is the record.