# CVE-2023-31147: Insufficient randomness in generation of DNS query IDs in c-ares

> Attackers can predict DNS query IDs due to weak randomness, enabling cache poisoning or spoofing attacks against applications using c-ares.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/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:** 25 May 2023
- **Updated:** 13 Feb 2025
- **Also known as:** AZL-26869, AZL-26870, AZL-26871, AZL-26874, AZL-26875, AZL-26876, AZL-34776, AZL-43702, DEBIAN-CVE-2023-31147, ECHO-ff3d-b3d4-b3c9, GHSA-8r8p-23f3-64c2, OESA-2023-1339, OESA-2023-1340

## What is CVE-2023-31147?

CVE-2023-31147 is a medium-severity vulnerability in Fedoraproject Fedora, published on 25 May 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

c-ares is an asynchronous resolver library. When /dev/urandom or RtlGenRandom() are unavailable, c-ares uses rand() to generate random numbers used for DNS query ids. This is not a CSPRNG, and it is also not seeded by srand() so will generate predictable output. Input from the random number generator is fed into a non-compilant RC4 implementation and may not be as strong as the original RC4 implementation. No attempt is made to look for modern OS-provided CSPRNGs like arc4random() that is widely available. This issue has been fixed in version 1.19.1.

Weakness: CWE-330 (Use of Insufficiently Random Values)

## Which versions are affected by CVE-2023-31147?

It affects 2 products.


Products: C-Ares Project C-Ares, Fedoraproject Fedora.

## How do I fix CVE-2023-31147?

Upgrade to a fixed version.

## Is CVE-2023-31147 being exploited?

There is no known exploitation of CVE-2023-31147 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2022-4904](https://insights.sbomify.com/CVE-2022-4904/): Memory corruption in c-ares (high 8.6)
- [CVE-2023-32067](https://insights.sbomify.com/CVE-2023-32067/): 0-byte UDP payload DoS in c-ares (high 7.5)
- [CVE-2020-8277](https://insights.sbomify.com/CVE-2020-8277/): Uncontrolled Resource Consumption in node (high 7.5)
- [CVE-2021-3672](https://insights.sbomify.com/CVE-2021-3672/): Other in c-ares (medium 5.6)
- [CVE-2023-31130](https://insights.sbomify.com/CVE-2023-31130/): Buffer Underwrite in ares_inet_net_pton() (medium 4.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-31147 and fix it if it is affected.

What it is: CVE-2023-31147 is a medium-severity vulnerability in Fedoraproject Fedora, published on 25 May 2023. 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-2023-31147 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-2023-31147/ (Markdown: https://insights.sbomify.com/CVE-2023-31147/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-31147
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-31147
- OSV: https://osv.dev/vulnerability/CVE-2023-31147

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-31147/
Summaries are generated and may contain mistakes; the official description above is the record.