Security researchers have recently uncovered three new vulnerabilities in the Sitecore Experience Platform, a popular enterprise-level content management system (CMS). These flaws, identified by watchTowr Labs, could be exploited by attackers to gain unauthorized access to information and execute malicious code on affected systems. The vulnerabilities, assigned CVE-2025-53693, CVE-2025-53691, and CVE-2025-53694, involve unsafe reflections leading to HTML cache poisoning, insecure deserialization resulting in remote code execution (RCE), and information disclosure through the ItemService API. Sitecore has already released patches for these issues, with the first two addressed in June and the third in July 2025, with the company stating that “successful exploitation of the related vulnerabilities might lead to remote code execution and non-authorized access to information.”
The most concerning aspect of these new findings is the potential for them to be combined into a sophisticated exploit chain. According to Piotr Bazydlo, a researcher at watchTowr Labs, an attacker could link the pre-auth HTML cache poisoning vulnerability (CVE-2025-53693) with a separate post-authenticated remote code execution vulnerability (CVE-2025-53691) to compromise even a fully patched instance of the Sitecore Experience Platform. This multi-step attack begins with the attacker leveraging the ItemService API, if exposed, to trivially enumerate HTML cache keys and send HTTP cache poisoning requests to those keys. This then allows them to supply malicious HTML that ultimately results in code execution by means of an unrestricted BinaryFormatter call.
The exploit chain is a prime example of how seemingly minor vulnerabilities can be leveraged for significant impact.
The first step involves exploiting the information disclosure vulnerability in the ItemService API (CVE-2025-53694). This allows an attacker, even with a restricted anonymous account, to brute-force and discover a list of valid cache keys. Once these keys are obtained, the attacker can use the HTML cache poisoning flaw (CVE-2025-53693) to inject malicious HTML into the pages corresponding to those keys. This is achieved by exploiting an “unsafe reflection path” that allows the attacker to poison any HTML cache key.
The final stage of the attack chain involves CVE-2025-53691, the remote code execution vulnerability. The malicious HTML code injected via the cache poisoning attack ultimately leads to an unrestricted BinaryFormatter call. This is a critical point of failure in the application’s design, as the BinaryFormatter class in .NET is known to be highly susceptible to insecure deserialization attacks. When an application deserializes untrusted data with BinaryFormatter, it can be tricked into executing arbitrary code. The injected HTML code is crafted to supply the malicious data that, upon deserialization, triggers this vulnerability, allowing the attacker to run commands on the server.
These new vulnerabilities are not isolated incidents; they build on previous security findings in the same product. Just in June, watchTowr Labs disclosed three other significant flaws in the Sitecore Experience Platform: CVE-2025-34509 (use of hard-coded credentials), CVE-2025-34510 (post-authenticated remote code execution via path traversal), and CVE-2025-34511 (post-authenticated RCE via Sitecore PowerShell Extension). The continued discovery of serious vulnerabilities highlights the ongoing challenges of securing complex enterprise-grade software. The ability to chain these flaws together, as demonstrated by Bazydlo, underscores the importance of a layered security approach and the need for organizations to apply patches promptly to mitigate the risk of a potential breach.
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