# CVE-2018-6594: Pycrypto generates weak key parameters

> Weak ElGamal key generation in PyCrypto allows attackers to recover sensitive information from ciphertext data.

- **Severity:** High 7.5 (`CVSS:3.0/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:** 3 Feb 2018
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2018-6594, GHSA-6528-wvf6-f6qg, MGASA-2018-0171, PYSEC-2018-97, UBUNTU-CVE-2018-6594, USN-3616-1

## What is CVE-2018-6594?

CVE-2018-6594 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 3 Feb 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

lib/Crypto/PublicKey/ElGamal.py in PyCrypto through 2.6.1 generates weak ElGamal key parameters, which allows attackers to obtain sensitive information by reading ciphertext data (i.e., it does not have semantic security in face of a ciphertext-only attack). The Decisional Diffie-Hellman (DDH) assumption does not hold for PyCrypto's ElGamal implementation.

Weakness: CWE-326 (Inadequate Encryption Strength)

## Which versions are affected by CVE-2018-6594?

3 open source packages ship an affected version, including pycrypto. It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pycrypto` | PyPI | All versions | None |
| `pycrypto` | PyPI | All versions to 2.6.1 | None |
| `pycrypto` | PyPI | All versions to 2.6.1 | None |

Products: Canonical Ubuntu Linux, Debian Debian Linux, Dlitz Pycrypto.

## How do I fix CVE-2018-6594?

Upgrade to a fixed version.

## Is CVE-2018-6594 being exploited?

There is no known exploitation of CVE-2018-6594 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-6594 and fix it if it is affected.

What it is: CVE-2018-6594 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 3 Feb 2018. 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-2018-6594 in the wild and no public exploit code.

Affected packages and fixed versions:
- pycrypto (PyPI): affected all versions; no fix listed
- pycrypto (PyPI): affected all versions up to 2.6.1; no fix listed
- pycrypto (PyPI): affected all versions up to 2.6.1; no fix listed

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-2018-6594/ (Markdown: https://insights.sbomify.com/CVE-2018-6594/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-6594
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-6594
- OSV: https://osv.dev/vulnerability/CVE-2018-6594

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-6594/
Summaries are generated and may contain mistakes; the official description above is the record.