# CVE-2020-35903: Out of bounds read in dync

> The dync crate allows misaligned memory access in VecCopy, potentially leading to crashes or arbitrary code execution in Rust applications.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Dec 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-qxjq-v4wf-ppvh, RUSTSEC-2020-0050

## What is CVE-2020-35903?

CVE-2020-35903 is a medium-severity memory corruption vulnerability in n/a, published on 31 Dec 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An issue was discovered in the dync crate before 0.5.0 for Rust. VecCopy allows misaligned element access because u8 is not always the type in question.

## Which versions are affected by CVE-2020-35903?

3 open source packages ship an affected version, including dync. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `dync` | crates.io | All versions | 0.5.0 |
| `dync` | crates.io | All versions | 0.5.0 |
| `dync` | crates.io | From 0.0.0-0 | 0.5.0 |

Products: Dync Project Dync.

## How do I fix CVE-2020-35903?

Upgrade dync to 0.5.0 or later.

## Is CVE-2020-35903 being exploited?

There is no known exploitation of CVE-2020-35903 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-35903 and fix it if it is affected.

What it is: CVE-2020-35903 is a medium-severity memory corruption vulnerability in n/a, published on 31 Dec 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-35903 in the wild and no public exploit code.

Affected packages and fixed versions:
- dync (crates.io): affected all versions; fixed in 0.5.0
- dync (crates.io): affected all versions; fixed in 0.5.0
- dync (crates.io): affected from 0.0.0-0; fixed in 0.5.0

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-2020-35903/ (Markdown: https://insights.sbomify.com/CVE-2020-35903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-35903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-35903
- OSV: https://osv.dev/vulnerability/CVE-2020-35903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-35903/
Summaries are generated and may contain mistakes; the official description above is the record.