CVE-2023-31147: c-ares is an asynchronous resolver library

Q: How do I fix CVE-2023-31147?

c-ares: upgrade to 1.19.1; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2023-31147 being exploited?

CVE-2023-31147 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2023-31147 affect?

CVE-2023-31147 affects c-ares, fedora. Severity is medium (CVSS 5.9). 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 genera

Q: How urgent is CVE-2023-31147?

Priority 41/100. Remotely exploitable, no login, no user action

This month

MEDIUM 5.9REMOTEUPGRADEMITIGATE

CVE-2023-31147 is a medium-severity flaw (CVSS 5.9) affecting c-ares, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-330
Published	2023-05-25
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: c-ares project · fedoraproject

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-05-25 22:15 UTCPublished CVE record published
2026-06-17 05:56 UTCUpdated Record last modified

c-ares project c-ares UPGRADE

Affected: < 1.19.1

Fixed in: 1.19.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy c-ares || rpm -q c-ares || c-ares --version

2. UPGRADE to 1.19.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade c-ares

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade c-ares

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 37 · 38

Fixed in: no fixed release known

Safe to downgrade to: a release before 37

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2023-31147?

c-ares: upgrade to 1.19.1; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-31147 being exploited?

CVE-2023-31147 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2023-31147 affect?

CVE-2023-31147 affects c-ares, fedora. Severity is medium (CVSS 5.9). 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 genera

How urgent is CVE-2023-31147?

Priority 41/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2025-62408 MEDIUM 5.9 UPGRADE c-ares is an asynchronous resolver library
CVE-2024-25629 MEDIUM 4.4 UPGRADE MITIGATE c-ares is a C library for asynchronous DNS requests
CVE-2023-32067 HIGH 7.5 UPGRADE MITIGATE c-ares is an asynchronous resolver library
CVE-2023-31130 MEDIUM 4.1 UPGRADE MITIGATE c-ares is an asynchronous resolver library
CVE-2023-31124 LOW 3.7 UPGRADE MITIGATE c-ares is an asynchronous resolver library

References

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