CVE-2006-6551: PHP remote file inclusion vulnerability in libs/tucows/api/cartridges/crt_TUCOWS_domains/lib/domainutils.inc.p

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HIGH 7.5DOWNGRADE

CVE-2006-6551 is a high-severity flaw (CVSS 7.5) affecting client code suite. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PHP remote file inclusion vulnerability in libs/tucows/api/cartridges/crt_TUCOWS_domains/lib/domainutils.inc.php in Tucows Client Code Suite (CCS) 1.2.1015 and earlier allows remote attackers to execute arbitrary PHP code via a URL in the _ENV[TCA_HOME] parameter.

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	2.2% (top 17%)
CISA exploited list	No
Published	2006-12-14
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: tucows

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2006-12-14 18:28 UTCPublished CVE record published
2026-06-16 22:33 UTCUpdated Record last modified

tucows client code suite DOWNGRADE

Affected: 1.2.1015

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.2.1015

1. Check installed version

apt-cache policy client-code-suite || rpm -q client-code-suite || client-code-suite --version

2. No fixed release: DOWNGRADE to a release before 1.2.1015 (Debian / Ubuntu)

apt-cache madison client-code-suite sudo apt install client-code-suite=<VERSION_BEFORE_1.2.1015> sudo apt-mark hold client-code-suite

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list client-code-suite sudo dnf downgrade client-code-suite-<VERSION_BEFORE_1.2.1015> sudo dnf versionlock add client-code-suite

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: Tucows Client Code Suite (CSS) 1.2.1015 - Remote File Inclusion

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-2006-6551?

client code suite: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2006-6551 being exploited?

CVE-2006-6551 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-2006-6551 affect?

CVE-2006-6551 affects client code suite. Severity is high (CVSS 7.5). PHP remote file inclusion vulnerability in libs/tucows/api/cartridges/crt_TUCOWS_domains/lib/domainutils.inc.php in Tucows Client Code Suite (CCS) 1.2.1015 and earlier allows remote attackers to execute arbitrary PHP code via a URL in the _

How urgent is CVE-2006-6551?

Priority 52/100. High severity; Public exploit reference

Software pages

PHP vulnerabilities

References

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