# CVE-2021-3923: Information disclosure in kernel

> A privileged local attacker can leak kernel stack information via RDMA commands, potentially bypassing kernel protection mechanisms.

- **Severity:** Low 2.3 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N`)
- **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:** 27 Mar 2023
- **Updated:** 24 Feb 2025
- **Also known as:** DEBIAN-CVE-2021-3923, GHSA-c8f9-2rww-56v5, UBUNTU-CVE-2021-3923

## What is CVE-2021-3923?

CVE-2021-3923 is a low-severity vulnerability in Fedoraproject Fedora, published on 27 Mar 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in the Linux kernel's implementation of RDMA over infiniband. An attacker with a privileged local account can leak kernel stack information when issuing commands to the /dev/infiniband/rdma_cm device node. While this access is unlikely to leak sensitive user information, it can be further used to defeat existing kernel protection mechanisms.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2021-3923?

It affects 3 products.


Products: Fedoraproject Fedora, Linux kernel, Redhat Enterprise Linux.

## How do I fix CVE-2021-3923?

Apply the vendor's patch.

## Is CVE-2021-3923 being exploited?

There is no known exploitation of CVE-2021-3923 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3923 and fix it if it is affected.

What it is: CVE-2021-3923 is a low-severity vulnerability in Fedoraproject Fedora, published on 27 Mar 2023. 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-2021-3923 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2021-3923/ (Markdown: https://insights.sbomify.com/CVE-2021-3923/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3923
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3923
- OSV: https://osv.dev/vulnerability/CVE-2021-3923

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3923/
Summaries are generated and may contain mistakes; the official description above is the record.