# CVE-2021-43045: Possible DOS vulnerabilities in C# Avro SDK

> An attacker can cause a denial-of-service by forcing excessive resource allocation in applications using the Apache Avro .NET SDK.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jan 2022
- **Updated:** 4 Aug 2024
- **Also known as:** CLSA-2026-1786345204, GHSA-868x-rg4c-cjqg, OESA-2023-1950

## What is CVE-2021-43045?

CVE-2021-43045 is a high-severity denial of service vulnerability in Apache Avro, published on 6 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the .NET SDK of Apache Avro allows an attacker to allocate excessive resources, potentially causing a denial-of-service attack. This issue affects .NET applications using Apache Avro version 1.10.2 and prior versions. Users should update to version 1.11.0 which addresses this issue.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2021-43045?

2 open source packages ship an affected version, including Apache.Avro. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Apache.Avro` | NuGet | All versions | 1.11.0 |
| `Apache.Avro` | NuGet | All versions | 1.11.0 |

Products: Apache Avro.

## How do I fix CVE-2021-43045?

Upgrade Apache.Avro to 1.11.0 or later.

## Is CVE-2021-43045 being exploited?

There is no known exploitation of CVE-2021-43045 in the wild and no public exploit code.

## Other vulnerabilities in Apache Avro

- [CVE-2024-47561](https://insights.sbomify.com/CVE-2024-47561/): Apache Avro Java SDK: Arbitrary Code Execution when reading Avro schema (Java SDK) (critical 9.2)
- [CVE-2023-39410](https://insights.sbomify.com/CVE-2023-39410/): Apache Avro Java SDK: Memory when deserializing untrusted data in Avro Java SDK (high 7.5)
- [CVE-2022-35724](https://insights.sbomify.com/CVE-2022-35724/): Denial of service while reading data in Avro Rust SDK (high 7.5)
- [CVE-2022-36124](https://insights.sbomify.com/CVE-2022-36124/): Memory overconsumption in Avro Rust SDK (high 7.5)
- [CVE-2022-36125](https://insights.sbomify.com/CVE-2022-36125/): Integer overflow when reading corrupted .avro file in Avro Rust SDK (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43045 and fix it if it is affected.

What it is: CVE-2021-43045 is a high-severity denial of service vulnerability in Apache Avro, published on 6 Jan 2022. 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-2021-43045 in the wild and no public exploit code.

Affected packages and fixed versions:
- Apache.Avro (NuGet): affected all versions; fixed in 1.11.0
- Apache.Avro (NuGet): affected all versions; fixed in 1.11.0

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-2021-43045/ (Markdown: https://insights.sbomify.com/CVE-2021-43045/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43045
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43045
- OSV: https://osv.dev/vulnerability/CVE-2021-43045

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43045/
Summaries are generated and may contain mistakes; the official description above is the record.