ThemeREX ShiftCV: PHP Object Injection in WordPress theme
Summary
The WordPress theme ShiftCV by ThemeREX, versions up to and including 3.0.14, contains a PHP Object Injection flaw (CWE-502) in the handling of serialized data. The flaw can be triggered without authentication over the network, so an attacker could manipulate how the site processes data. Patchstack and CISA SSVC rate the impact as total, and code execution is plausible depending on the installed code, but this is not confirmed.
Affected
- WordPress theme ShiftCV by ThemeREX, versions up to and including 3.0.14
- Default configuration: unaffected (per CNA record)
Fixed in
- Unknown. Patchstack lists no official patch. The research notes mention version 3.0.15 from a secondary source, which is not confirmed by the vendor.
Workaround
- Unknown. No vendor workaround found.
- Patchstack has issued a mitigation rule (virtual patch) that blocks attacks until an official patch is available.
- If the theme is not active, removing or deactivating it removes the exposure.
Exploitation
- Not marked as known exploited (not in CISA KEV, per the research notes).
- CISA SSVC in the CNA data: exploitation none, automatable yes, technical impact total.
- Patchstack describes the flaw as expected to become exploited and used in mass-exploit campaigns.
- EPSS: 0.00304.
- No public proof of concept found; treat as unknown, not as absent.
Our recommendation
- Inventory WordPress sites and check the installed ShiftCV version under Appearance > Themes.
- Remove or deactivate the theme on sites where it is not needed.
- Where the theme is needed and no official patch exists, apply a WAF or Patchstack virtual patch and monitor logs.
- Check exposed sites for compromise indicators: unexpected admin accounts, modified files, unknown PHP files in uploads.
- Review hosting and backups, and check for a fixed version once the vendor publishes one.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Patchstack advisory (CNA) patchstack.com
- OpenCVE CVE-2026-66564 app.opencve.io
- VulDB CVE-2026-66564 vuldb.com
- Vulners (Rapid7) CVE-2026-66564 with EPSS vulners.com
- HOL Guard CVE-2026-66564 hol.org
- ThemeREX ShiftCV product page themerex.net
- ShiftCV on ThemeForest themeforest.net
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 19:28.
Original description (NVD)
Unauthenticated PHP Object Injection in ShiftCV <= 3.0.14 versions.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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