CVE-2026-45247

Mirasvit Full Page Cache Warmer, a storefront performance extension for Magento, contains a PHP deserialization flaw (CWE-502) that permits unauthenticated remote code execution. The flaw is triggered simply by sending the store a request carrying a crafted serialized PHP object in the 'CacheWarmer' cookie; when the application unserializes that untrusted value, attacker-controlled object injection executes code in the context of the web server. Successful exploitation yields arbitrary code execution on the storefront host, useful for webshell deployment, data theft, or lateral movement, and it requires no credentials or special privileges. Any site running the extension is affected; no public proof-of-concept is known, but CISA added the flaw to the Known Exploited Vulnerabilities catalog on 2026-06-03, confirming exploitation in the wild (ransomware use unknown), and EPSS assigns a 27.5% 30-day exploitation probability (98th percentile).

What to do: Apply Mirasvit's remediation guidance and upgrade the Full Page Cache Warmer extension as soon as the vendor publishes a fixed release; the KEV listing (2026-06-03) makes patching or mitigation mandatory for U.S. federal agencies under BOD 22-01. Until patched, hunt for exploitation by reviewing web access logs for anomalous or oversized 'CacheWarmer' cookie values containing serialized PHP objects (e.g., 'O:'-prefixed payloads) and for indicators of post-exploitation on Magento web servers. If no fix is available yet and the store is internet-facing, consider temporarily disabling the extension or restricting the CacheWarmer cookie handling as an interim mitigation.