# CVE-2021-3505: Weak cryptography in libtpms

> A flaw in libtpms causes RSA keys to have reduced strength, potentially compromising data confidentiality for users of the TPM 2 implementation.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **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:** 19 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-3505, GHSA-239j-gmhr-4pcm, OESA-2022-1959

## What is CVE-2021-3505?

CVE-2021-3505 is a medium-severity vulnerability in Fedoraproject Fedora, published on 19 Apr 2021. 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 libtpms in versions before 0.8.0. The TPM 2 implementation returns 2048 bit keys with ~1984 bit strength due to a bug in the TCG specification. The bug is in the key creation algorithm in RsaAdjustPrimeCandidate(), which is called before the prime number check. The highest threat from this vulnerability is to data confidentiality.

Weakness: CWE-331 (Insufficient Entropy)

## Which versions are affected by CVE-2021-3505?

It affects 3 products.


Products: Fedoraproject Fedora, Libtpms Project Libtpms, Redhat Enterprise Linux.

## How do I fix CVE-2021-3505?

Upgrade to a fixed version.

## Is CVE-2021-3505 being exploited?

There is no known exploitation of CVE-2021-3505 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-2021-3505 and fix it if it is affected.

What it is: CVE-2021-3505 is a medium-severity vulnerability in Fedoraproject Fedora, published on 19 Apr 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-2021-3505 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-2021-3505/ (Markdown: https://insights.sbomify.com/CVE-2021-3505/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3505
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3505
- OSV: https://osv.dev/vulnerability/CVE-2021-3505

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3505/
Summaries are generated and may contain mistakes; the official description above is the record.