# CVE-2021-4160: BN_mod_exp may produce incorrect results on MIPS

> A carry propagation bug in OpenSSL on MIPS platforms may allow attackers to deduce private key information from Diffie-Hellman operations.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/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:** 28 Jan 2022
- **Updated:** 16 Sep 2024
- **Also known as:** AZL-8472, DEBIAN-CVE-2021-4160, GHSA-ph2x-8239-7xc7, JLSEC-2026-226, UBUNTU-CVE-2021-4160

## What is CVE-2021-4160?

CVE-2021-4160 is a medium-severity vulnerability in Debian Debian Linux, published on 28 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

There is a carry propagation bug in the MIPS32 and MIPS64 squaring procedure. Many EC algorithms are affected, including some of the TLS 1.3 default curves. Impact was not analyzed in detail, because the pre-requisites for attack are considered unlikely and include reusing private keys. Analysis suggests that attacks against RSA and DSA as a result of this defect would be very difficult to perform and are not believed likely. Attacks against DH are considered just feasible (although very difficult) because most of the work necessary to deduce information about a private key may be performed offline. The amount of resources required for such an attack would be significant. However, for an attack on TLS to be meaningful, the server would have to share the DH private key among multiple clients, which is no longer an option since CVE-2016-0701. This issue affects OpenSSL versions 1.0.2, 1.1.1 and 3.0.0. It was addressed in the releases of 1.1.1m and 3.0.1 on the 15th of December 2021. For the 1.0.2 release it is addressed in git commit 6fc1aaaf3 that is available to premium support customers only. It will be made available in 1.0.2zc when it is released. The issue only affects OpenSSL on MIPS platforms. Fixed in OpenSSL 3.0.1 (Affected 3.0.0). Fixed in OpenSSL 1.1.1m (Affected 1.1.1-1.1.1l). Fixed in OpenSSL 1.0.2zc-dev (Affected 1.0.2-1.0.2zb).

## Which versions are affected by CVE-2021-4160?

It affects 8 products.


Products: Debian Debian Linux, Openssl Openssl, Oracle Enterprise Manager Ops Center, Oracle Health Sciences Inform Publisher, Oracle Jd Edwards Enterpriseone Tools, Oracle Jd Edwards World Security, Oracle Peoplesoft Enterprise Peopletools, Siemens Sinec Ins.

## How do I fix CVE-2021-4160?

Upgrade to a fixed version.

## Is CVE-2021-4160 being exploited?

There is no known exploitation of CVE-2021-4160 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4160 and fix it if it is affected.

What it is: CVE-2021-4160 is a medium-severity vulnerability in Debian Debian Linux, published on 28 Jan 2022. 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-2021-4160 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-4160/ (Markdown: https://insights.sbomify.com/CVE-2021-4160/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4160
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4160
- OSV: https://osv.dev/vulnerability/CVE-2021-4160

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4160/
Summaries are generated and may contain mistakes; the official description above is the record.