CVE-2020-17952: A remote code execution (RCE) vulnerability in /library/think/App.php of Twothink v2.0 allows attackers to exe

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2020-17952 is a critical-severity flaw (CVSS 9.8) affecting twothink. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A remote code execution (RCE) vulnerability in /library/think/App.php of Twothink v2.0 allows attackers to execute arbitrary PHP code.

Why this priority

Critical severity
Public exploit reference
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	2.5% (top 15%)
CISA exploited list	No
Published	2021-07-26
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: twothink project

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

Am I affected?

Timeline

2021-07-26 20:15 UTCPublished CVE record published
2026-06-17 02:59 UTCUpdated Record last modified

twothink project twothink DOWNGRADE

Affected: 2.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.0 (Debian / Ubuntu)

apt-cache madison twothink sudo apt install twothink=<VERSION_BEFORE_2.0> sudo apt-mark hold twothink

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

dnf --showduplicates list twothink sudo dnf downgrade twothink-<VERSION_BEFORE_2.0> sudo dnf versionlock add twothink

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-2020-17952?

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

Is CVE-2020-17952 being exploited?

CVE-2020-17952 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-2020-17952 affect?

CVE-2020-17952 affects twothink. Severity is critical (CVSS 9.8). A remote code execution (RCE) vulnerability in /library/think/App.php of Twothink v2.0 allows attackers to execute arbitrary PHP code.

How urgent is CVE-2020-17952?

Priority 65/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

References

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