# CVE-2023-42809: Redisson unsafe deserialization vulnerability

> Attackers can execute arbitrary code on client machines by tricking them into connecting to a malicious Redis server that sends crafted serialized objects.

- **Severity:** Critical 9.7 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 4 Oct 2023
- **Updated:** 19 Sep 2024
- **Also known as:** GHSA-4hvc-qwr2-f8rv

## What is CVE-2023-42809?

CVE-2023-42809 is a critical unsafe deserialization vulnerability in redisson, published on 4 Oct 2023. 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

Redisson is a Java Redis client that uses the Netty framework. Prior to version 3.22.0, some of the messages received from the Redis server contain Java objects that the client deserializes without further validation. Attackers that manage to trick clients into communicating with a malicious server can include especially crafted objects in its responses that, once deserialized by the client, force it to execute arbitrary code. This can be abused to take control of the machine the client is running in. Version 3.22.0 contains a patch for this issue.

Some post-fix advice is available. Do NOT use `Kryo5Codec` as deserialization codec, as it is still vulnerable to arbitrary object deserialization due to the `setRegistrationRequired(false)` call. On the contrary, `KryoCodec` is safe to use. The fix applied to `SerializationCodec` only consists of adding an optional allowlist of class names, even though making this behavior the default is recommended. When instantiating `SerializationCodec` please use the `SerializationCodec(ClassLoader classLoader, Set<String> allowedClasses)` constructor to restrict the allowed classes for deserialization.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2023-42809?

2 open source packages ship an affected version, including org.redisson:redisson. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.redisson:redisson` | Maven | All versions | 3.22.0 |
| `org.redisson:redisson` | Maven | All versions | 3.22.0 |

Products: Redisson Redisson.

## How do I fix CVE-2023-42809?

Upgrade org.redisson:redisson to 3.22.0 or later.

## Is CVE-2023-42809 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-42809 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-42809 and fix it if it is affected.

What it is: CVE-2023-42809 is a critical unsafe deserialization vulnerability in redisson, published on 4 Oct 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-42809 exists.

Affected packages and fixed versions:
- org.redisson:redisson (Maven): affected all versions; fixed in 3.22.0
- org.redisson:redisson (Maven): affected all versions; fixed in 3.22.0

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-2023-42809/ (Markdown: https://insights.sbomify.com/CVE-2023-42809/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-42809
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-42809
- OSV: https://osv.dev/vulnerability/CVE-2023-42809

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-42809/
Summaries are generated and may contain mistakes; the official description above is the record.