CVE-2020-5203: In Fat-Free Framework 3.7.1, attackers can achieve arbitrary code execution if developers choose to pass user

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2020-5203 is a critical-severity flaw (CVSS 9.8) affecting fat-free framework. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Fat-Free Framework 3.7.1, attackers can achieve arbitrary code execution if developers choose to pass user controlled input (e.g., $_REQUEST, $_GET, or $_POST) to the framework's Clear method.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.1% (top 18%)
CISA exploited list	No
Weakness	CWE-20, CWE-94
Published	2020-03-11
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fatfreeframework

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

Am I affected?

Timeline

2020-03-11 14:15 UTCPublished CVE record published
2026-06-17 03:21 UTCUpdated Record last modified

fatfreeframework fat-free framework DOWNGRADE

Affected: 3.7.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.7.1

1. Check installed version

apt-cache policy fat-free-framework || rpm -q fat-free-framework || fat-free-framework --version

2. No fixed release: DOWNGRADE to a release before 3.7.1 (Debian / Ubuntu)

apt-cache madison fat-free-framework sudo apt install fat-free-framework=<VERSION_BEFORE_3.7.1> sudo apt-mark hold fat-free-framework

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

dnf --showduplicates list fat-free-framework sudo dnf downgrade fat-free-framework-<VERSION_BEFORE_3.7.1> sudo dnf versionlock add fat-free-framework

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-2020-5203?

fat-free framework: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-5203 being exploited?

CVE-2020-5203 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-2020-5203 affect?

CVE-2020-5203 affects fat-free framework. Severity is critical (CVSS 9.8). In Fat-Free Framework 3.7.1, attackers can achieve arbitrary code execution if developers choose to pass user controlled input (e.g., $_REQUEST, $_GET, or $_POST) to the framework's Clear method.

How urgent is CVE-2020-5203?

Priority 60/100. Critical severity; Remotely exploitable, no login, no user action

References

← Back to latest CVEs