CVE-2021-31702: Frontier ichris through 5.18 mishandles making a DNS request for the hostname in the HTTP Host header, as demo

Q: How do I fix CVE-2021-31702?

ichris: upgrade to newer than 5.18. Exact commands for each OS are on this page.

Q: Is CVE-2021-31702 being exploited?

CVE-2021-31702 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-2021-31702 affect?

CVE-2021-31702 affects ichris. Severity is high (CVSS 7.5). Frontier ichris through 5.18 mishandles making a DNS request for the hostname in the HTTP Host header, as demonstrated by submitting 127.0.0.1 multiple times for DoS.

Q: How urgent is CVE-2021-31702?

Priority 54/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2021-31702 is a high-severity flaw (CVSS 7.5) affecting ichris. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Frontier ichris through 5.18 mishandles making a DNS request for the hostname in the HTTP Host header, as demonstrated by submitting 127.0.0.1 multiple times for DoS.

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	1.2% (top 31%)
CISA exploited list	No
Published	2021-05-29
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: frontiersoftware

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

Am I affected?

Timeline

2021-05-29 14:15 UTCPublished CVE record published
2026-06-17 03:52 UTCUpdated Record last modified

frontiersoftware ichris UPGRADE

Affected: <= 5.18

Fixed in: newer than 5.18

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 5.18 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ichris

Note

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

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-2021-31702?

ichris: upgrade to newer than 5.18. Exact commands for each OS are on this page.

Is CVE-2021-31702 being exploited?

CVE-2021-31702 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-2021-31702 affect?

CVE-2021-31702 affects ichris. Severity is high (CVSS 7.5). Frontier ichris through 5.18 mishandles making a DNS request for the hostname in the HTTP Host header, as demonstrated by submitting 127.0.0.1 multiple times for DoS.

How urgent is CVE-2021-31702?

Priority 54/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-31703 CRITICAL 9.8 UPGRADE Frontier ichris through 5.18 allows users to upload malicious executable files that might later be downloaded

References

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