Description

Unauthenticated PHP Object Injection in The Events Calendar <= 6.17.2 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-08-24T22:17:20.407Z",
  "pubdate": "2026-08-24T22:17:20.407Z",
  "executiveSummary": "An unauthenticated PHP Object Injection vulnerability has been identified in The Events Calendar plugin, specifically affecting versions 6.17.2 and prior.\nThe vulnerability allows remote, unauthenticated attackers to supply maliciously crafted serialized data to vulnerable endpoints processed by the application.\nSuccessful exploitation of this flaw can lead to severe security implications, including arbitrary code execution, remote code execution (RCE), SQL injection, or file deletion, depending on the presence of suitable gadget chains within the application scope or included third-party libraries.\nThe risk implication is critical due to the lack of authentication requirements, allowing any network-adjacent or remote attacker to interact directly with the vulnerable input handling mechanism without prior access credentials.\nExploitation requirements include the exposure of the vulnerable PHP endpoint handling unserialization operations and the availability of viable gadget chains within the PHP application environment to achieve post-exploitation execution objectives.",
  "technicalDetails": "The root cause of the vulnerability stems from the insecure handling of user-supplied data that is passed directly into native PHP unserialization functions such as unserialize() without proper validation, sanitization, or type checking within The Events Calendar plugin.\nVulnerable component logic fails to ensure that input strings originating from HTTP requests are safe from deserialization tampering, thereby exposing internal object instantiation mechanisms to external manipulation.\nAffected versions comprise The Events Calendar <= 6.17.2, operating under network exposure where HTTP requests can reach the vulnerable handlers.\nAuthentication requirements are entirely absent, as the vulnerability is exploitable by unauthenticated threat actors over the network.\nPrivilege requirements are nonexistent; the attack can be executed by any external entity capable of transmitting an HTTP request containing the malicious payload to the target WordPress installation.\nThe attack flow proceeds as follows: First, the attacker crafts a malicious serialized PHP object string designed to leverage existing classes (gadgets) within the PHP application landscape that implement magic methods such as __destruct(), __wakeup(), or __toString().\nSecond, the attacker transmits this serialized payload via HTTP GET or POST parameters to the vulnerable endpoint within The Events Calendar.\nThird, the application ingests the input and invokes the insecure unserialize() function upon the malicious payload.\nFourth, PHP instantiates the objects defined within the payload and automatically triggers the associated magic methods during the object lifecycle.\nFifth, payload behavior executes the underlying logic embedded within the gadget chain, potentially leading to arbitrary file operations, database interactions, or direct system command execution depending on the specific gadget classes loaded in memory.\nPost-exploitation impact ranges from complete system compromise via remote code execution to data exfiltration and integrity degradation, contingent upon the privileges of the web server user and the available application gadgets."
}