CVE-2023-31606: A Regular Expression Denial of Service (ReDoS) issue was discovered in the sanitize_html function of redcloth

This week

HIGH 7.5REMOTEUPGRADE

CVE-2023-31606 is a high-severity flaw (CVSS 7.5) affecting redcloth. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A Regular Expression Denial of Service (ReDoS) issue was discovered in the sanitize_html function of redcloth gem v4.0.0. This vulnerability allows attackers to cause a Denial of Service (DoS) via supplying a crafted payload.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-1333
Published	2023-06-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: promptworks

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

Am I affected?

Timeline

2023-06-06 17:15 UTCPublished CVE record published
2026-06-17 05:57 UTCUpdated Record last modified

promptworks redcloth UPGRADE

Affected: >= 4.0.0 and <= 4.3.2

Fixed in: newer than 4.3.2

Safe to downgrade to: a release before 4.0.0

1. Check installed version

apt-cache policy redcloth || rpm -q redcloth || redcloth --version

2. UPGRADE to newer than 4.3.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade redcloth

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade redcloth

Note

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

3. If no update is available yet, DOWNGRADE to a release before 4.0.0 (Debian / Ubuntu)

apt-cache madison redcloth sudo apt install redcloth=<VERSION_BEFORE_4.0.0> sudo apt-mark hold redcloth

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list redcloth sudo dnf downgrade redcloth-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add redcloth

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2023-31606?

redcloth: upgrade to newer than 4.3.2. Exact commands for each OS are on this page.

Is CVE-2023-31606 being exploited?

CVE-2023-31606 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-2023-31606 affect?

CVE-2023-31606 affects redcloth. Severity is high (CVSS 7.5). A Regular Expression Denial of Service (ReDoS) issue was discovered in the sanitize_html function of redcloth gem v4.0.0. This vulnerability allows attackers to cause a Denial of Service (DoS) via supplying a crafted payload.

How urgent is CVE-2023-31606?

Priority 55/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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