# CVE-2020-35711: Dangling reference in `access::Map` with Constant

> A use-after-free vulnerability in the arc-swap Rust library allows attackers to trigger dangling references, potentially leading to crashes or arbitrary code execution.

- **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:** 25 Dec 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-35711, GHSA-9pqx-g3jh-qpqq, RUSTSEC-2020-0091, UBUNTU-CVE-2020-35711

## What is CVE-2020-35711?

CVE-2020-35711 is a high-severity use after free vulnerability in n/a, published on 25 Dec 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue has been discovered in the arc-swap crate before 0.4.8 (and 1.x before 1.1.0) for Rust. Use of arc_swap::access::Map with the Constant test helper (or with a user-supplied implementation of the Access trait) could sometimes lead to dangling references being returned by the map.

## Which versions are affected by CVE-2020-35711?

5 open source packages ship an affected version, including arc-swap. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `arc-swap` | crates.io | From 0.4.2 | 0.4.8, 1.1.0 |
| `arc-swap` | crates.io | From 0.4.2 | 0.4.8 |
| `arc-swap` | crates.io | From 0.4.2 | 0.4.8 |
| `arc-swap` | crates.io | From 1.0.0 | 1.1.0 |
| `arc-swap` | crates.io | From 1.0.0 | 1.1.0 |

Products: Arc-Swap Project Arc-Swap.

## How do I fix CVE-2020-35711?

Upgrade arc-swap to a fixed version for your release line: 0.4.8 or 1.1.0.

## Is CVE-2020-35711 being exploited?

There is no known exploitation of CVE-2020-35711 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-35711 and fix it if it is affected.

What it is: CVE-2020-35711 is a high-severity use after free vulnerability in n/a, published on 25 Dec 2020. 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-2020-35711 in the wild and no public exploit code.

Affected packages and fixed versions:
- arc-swap (crates.io): affected from 0.4.2; fixed in 0.4.8, 1.1.0
- arc-swap (crates.io): affected from 0.4.2; fixed in 0.4.8
- arc-swap (crates.io): affected from 0.4.2; fixed in 0.4.8
- arc-swap (crates.io): affected from 1.0.0; fixed in 1.1.0
- arc-swap (crates.io): affected from 1.0.0; fixed in 1.1.0

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-2020-35711/ (Markdown: https://insights.sbomify.com/CVE-2020-35711/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-35711
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-35711
- OSV: https://osv.dev/vulnerability/CVE-2020-35711

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-35711/
Summaries are generated and may contain mistakes; the official description above is the record.