# CVE-2020-27835: Use after free in kernel

> A local attacker can crash the system via a use-after-free flaw in the Linux kernel infiniband hfi1 driver.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Jan 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-27835, GHSA-8pf6-658f-7qh2, UBUNTU-CVE-2020-27835

## What is CVE-2020-27835?

CVE-2020-27835 is a medium-severity use after free vulnerability in kernel, published on 7 Jan 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A use after free in the Linux kernel infiniband hfi1 driver in versions prior to 5.10-rc6 was found in the way user calls Ioctl after open dev file and fork. A local user could use this flaw to crash the system.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2020-27835?

It affects 1 product.


Products: Linux Infiniband Hfi1 Driver.

## How do I fix CVE-2020-27835?

Apply the vendor's patch.

## Is CVE-2020-27835 being exploited?

There is no known exploitation of CVE-2020-27835 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27835 and fix it if it is affected.

What it is: CVE-2020-27835 is a medium-severity use after free vulnerability in kernel, published on 7 Jan 2021. 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-2020-27835 in the wild and no public exploit code.

Affected product: kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2020-27835/ (Markdown: https://insights.sbomify.com/CVE-2020-27835/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27835
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27835
- OSV: https://osv.dev/vulnerability/CVE-2020-27835

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-27835/
Summaries are generated and may contain mistakes; the official description above is the record.