CVE-2017-12856: Cross-site scripting (XSS) vulnerability in C.P.Sub 5.2 allows remote attackers to inject arbitrary web script

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MEDIUM 6.1DOWNGRADE

CVE-2017-12856 is a medium-severity flaw (CVSS 6.1) affecting c.p.sub. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cross-site scripting (XSS) vulnerability in C.P.Sub 5.2 allows remote attackers to inject arbitrary web script or HTML via the keyword parameter to index.php.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.8% (top 43%)
CISA exploited list	No
Weakness	CWE-79
Published	2017-08-29
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: c.p.sub project

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

Am I affected?

Timeline

2017-08-29 15:29 UTCPublished CVE record published
2026-06-17 01:04 UTCUpdated Record last modified

c.p.sub project c.p.sub DOWNGRADE

Affected: 5.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.2

1. Check installed version

apt-cache policy c.p.sub || rpm -q c.p.sub || c.p.sub --version

2. No fixed release: DOWNGRADE to a release before 5.2 (Debian / Ubuntu)

apt-cache madison c.p.sub sudo apt install c.p.sub=<VERSION_BEFORE_5.2> sudo apt-mark hold c.p.sub

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

dnf --showduplicates list c.p.sub sudo dnf downgrade c.p.sub-<VERSION_BEFORE_5.2> sudo dnf versionlock add c.p.sub

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-2017-12856?

c.p.sub: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2017-12856 being exploited?

CVE-2017-12856 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-2017-12856 affect?

CVE-2017-12856 affects c.p.sub. Severity is medium (CVSS 6.1). Cross-site scripting (XSS) vulnerability in C.P.Sub 5.2 allows remote attackers to inject arbitrary web script or HTML via the keyword parameter to index.php.

How urgent is CVE-2017-12856?

Priority 41/100. Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2019-7738 MEDIUM 6.5 UPGRADE C.P.Sub before 5.3 allows CSRF via a manage.php?p=article_del&id= URI.

References

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