CVE-2021-24857: The ToTop Link WordPress plugin through 1.7.1 passes base64 encoded user input to the unserialize() PHP functi

Q: How do I fix CVE-2021-24857?

totop link: upgrade to newer than 1.7.1. Exact commands for each OS are on this page.

Q: Is CVE-2021-24857 being exploited?

CVE-2021-24857 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-2021-24857 affect?

CVE-2021-24857 affects totop link. Severity is critical (CVSS 9.8). The ToTop Link WordPress plugin through 1.7.1 passes base64 encoded user input to the unserialize() PHP function, which could lead to PHP Object injection if a plugin installed on the blog has a suitable gadget chain.

Q: How urgent is CVE-2021-24857?

Priority 64/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-24857 is a critical-severity flaw (CVSS 9.8) affecting totop link. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The ToTop Link WordPress plugin through 1.7.1 passes base64 encoded user input to the unserialize() PHP function, which could lead to PHP Object injection if a plugin installed on the blog has a suitable gadget chain.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.9% (top 20%)
CISA exploited list	No
Weakness	CWE-502
Published	2021-12-13
Last modified	2026-06-17

Publisher (CNA): WPScan · Vendor: nocean

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

Am I affected?

Timeline

2021-12-13 11:15 UTCPublished CVE record published
2026-06-17 03:41 UTCUpdated Record last modified

nocean totop link UPGRADE

Affected: <= 1.7.1

Fixed in: newer than 1.7.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy totop-link || rpm -q totop-link || totop-link --version

2. UPGRADE to newer than 1.7.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade totop-link

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade totop-link

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-2021-24857?

totop link: upgrade to newer than 1.7.1. Exact commands for each OS are on this page.

Is CVE-2021-24857 being exploited?

CVE-2021-24857 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-2021-24857 affect?

CVE-2021-24857 affects totop link. Severity is critical (CVSS 9.8). The ToTop Link WordPress plugin through 1.7.1 passes base64 encoded user input to the unserialize() PHP function, which could lead to PHP Object injection if a plugin installed on the blog has a suitable gadget chain.

How urgent is CVE-2021-24857?

Priority 64/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

WordPress vulnerabilities · PHP vulnerabilities

References

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