ToTop Link <= 1.7.1 - Unauthenticated PHP Object Injection
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- ToTop Link
- Affected Version
<= 1.7.1- CVSS
- 9.0Critical
- Weakness type
- CWE-502 · Deserialization of Untrusted Data
- CVE
CVE-2021-24857
At a glance
CVE-2021-24857 is a critical-severity Deserialization of Untrusted Data vulnerability in the ToTop Link WordPress plugin, affecting versions <= 1.7.1. It carries a CVSS score of 9.0 (reachable over the network; high confidentiality, integrity, availability impact). Exploitation requires no authentication. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed November 2021, reported by Muhammed Kara.
Vulnerability Overview
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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, and no privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.
CWE-502: Deserialization of Untrusted Data
ToTop Link <= 1.7.1 carries this weakness at unserialize(), and reaching it takes no account at all. Deserialization of untrusted data means the application reconstructs objects from input a caller controls, letting the attacker choose which classes get instantiated and what their properties hold.
A workable chain turns deserialization into file writes, deletions or code execution, depending on what the loaded classes do in their magic methods. No fixed build of this plugin is recorded for ToTop Link yet, so installs running <= 1.7.1 stay exposed until the vendor ships one.
Remediation
No known patch available. Please review the vulnerability's details in depth and employ mitigations based on your organization's risk tolerance. It may be best to uninstall the affected software and find a replacement.
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Scanner
- Login Security
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C