# CVE-2021-45451: Security feature bypass in n/a

> Attackers can bypass cryptographic policies or decrypt data via oracle attacks in Mbed TLS when nonce generation buffers are accessible to untrusted applications.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-2grh-pj67-4p6p, JLSEC-2025-216

## What is CVE-2021-45451?

CVE-2021-45451 is a high-severity vulnerability in Arm Mbed Tls, published on 21 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In Mbed TLS before 3.1.0, psa_aead_generate_nonce allows policy bypass or oracle-based decryption when the output buffer is at memory locations accessible to an untrusted application.

Weakness: CWE-327 (Use of a Broken or Risky Cryptographic Algorithm)

## Which versions are affected by CVE-2021-45451?

It affects 2 products.


Products: Arm Mbed Tls, Fedoraproject Fedora.

## How do I fix CVE-2021-45451?

Upgrade to a fixed version.

## Is CVE-2021-45451 being exploited?

There is no known exploitation of CVE-2021-45451 in the wild and no public exploit code.

## Other vulnerabilities in Arm Mbed Tls

- [CVE-2026-34877](https://insights.sbomify.com/CVE-2026-34877/): Deserialization in n/a (critical 9.8)
- [CVE-2022-46393](https://insights.sbomify.com/CVE-2022-46393/): Memory corruption in n/a (critical 9.8)
- [CVE-2021-44732](https://insights.sbomify.com/CVE-2021-44732/): Use after free in n/a (critical 9.8)
- [CVE-2017-18187](https://insights.sbomify.com/CVE-2017-18187/): Integer overflow in n/a (critical 9.8)
- [CVE-2018-0487](https://insights.sbomify.com/CVE-2018-0487/): Memory corruption in ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0 (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-45451 and fix it if it is affected.

What it is: CVE-2021-45451 is a high-severity vulnerability in Arm Mbed Tls, published on 21 Dec 2021. 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-2021-45451 in the wild and no public exploit code.

Affected product: Arm Mbed Tls. 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-2021-45451/ (Markdown: https://insights.sbomify.com/CVE-2021-45451/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-45451
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-45451
- OSV: https://osv.dev/vulnerability/CVE-2021-45451

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-45451/
Summaries are generated and may contain mistakes; the official description above is the record.