Flickr Gallery <= 1.5.2 - Unauthenticated PHP Object Injection
Strategic Overview
- Status
- Patched in 1.5.3
- Affected Plugin
- Flickr Gallery
- Affected Version
< 1.5.3- CVSS
- 9.8Critical
- Weakness type
- CWE-502 · Deserialization of Untrusted Data
- CVE
CVE-2017-20207
At a glance
CVE-2017-20207 is a critical-severity Deserialization of Untrusted Data vulnerability in the Flickr Gallery WordPress plugin, affecting versions < 1.5.3. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 1.5.3; sites on affected versions should update now. Disclosed October 2017, reported by Matt Barry.
Vulnerability Overview
The Flickr Gallery plugin for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 1.5.2 via deserialization of untrusted input from the `pager ` parameter. This allows unauthenticated attackers to inject a PHP Object. Attackers were actively exploiting this vulnerability with the WP_Theme() class to create backdoors.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, 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
Flickr Gallery < 1.5.3 carries this weakness at WP_Theme(), 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. For Flickr Gallery the fix is 1.5.3: builds < 1.5.3 are affected, anything from 1.5.3 onward is not.
Remediation
Update to version 1.5.3, or a newer patched version
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. None of that substitutes for the fix: Flickr Gallery 1.5.3 closes this, and updating the plugin is the step that ends it.
- Firewall
- Scanner
- Login Security
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C