CVE-2020-26768: Formstone <=1.4.16 is vulnerable to a Reflected Cross-Site Scripting (XSS) vulnerability caused by improper va

Q: How do I fix CVE-2020-26768?

formstone: upgrade to newer than 1.4.16. Exact commands for each OS are on this page.

Q: Is CVE-2020-26768 being exploited?

CVE-2020-26768 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-2020-26768 affect?

CVE-2020-26768 affects formstone. Severity is medium (CVSS 6.1). Formstone <=1.4.16 is vulnerable to a Reflected Cross-Site Scripting (XSS) vulnerability caused by improper validation of user supplied input in the upload-target.php and upload-chunked.php files. A remote attacker could exploit this vulner

Q: How urgent is CVE-2020-26768?

Priority 39/100. No elevated risk signals yet.

Routine

MEDIUM 6.1UPGRADE

CVE-2020-26768 is a medium-severity flaw (CVSS 6.1) affecting formstone. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Formstone <=1.4.16 is vulnerable to a Reflected Cross-Site Scripting (XSS) vulnerability caused by improper validation of user supplied input in the upload-target.php and upload-chunked.php files. A remote attacker could exploit this vulnerability using a specially crafted URL to execute a script in a victim's Web browser within the security context of the hosting Web site once the URL is clicked or visited. An attacker could use this vulnerabili

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.3% (top 30%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-01-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: formstone

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

Am I affected?

Timeline

2021-01-07 13:15 UTCPublished CVE record published
2026-06-17 03:08 UTCUpdated Record last modified

formstone formstone UPGRADE

Affected: <= 1.4.16

Fixed in: newer than 1.4.16

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.4.16 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade formstone

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-2020-26768?

formstone: upgrade to newer than 1.4.16. Exact commands for each OS are on this page.

Is CVE-2020-26768 being exploited?

CVE-2020-26768 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-2020-26768 affect?

CVE-2020-26768 affects formstone. Severity is medium (CVSS 6.1). Formstone <=1.4.16 is vulnerable to a Reflected Cross-Site Scripting (XSS) vulnerability caused by improper validation of user supplied input in the upload-target.php and upload-chunked.php files. A remote attacker could exploit this vulner

How urgent is CVE-2020-26768?

Priority 39/100. No elevated risk signals yet.

Software pages

PHP vulnerabilities

References

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