CVE-2025-53690: Sitecore Multiple Products Deserialization of Untrusted Data Vulnerability

CVE-2025-53690 is a deserialization of untrusted data vulnerability affecting multiple Sitecore products, including Experience Manager (XM), Experience Platform (XP), Experience Commerce (XC), and Managed Cloud. It involves the use of default ASP.NET machine keys that can be exploited to achieve remote code execution. This matters because successful abuse can give an attacker full control of the affected Sitecore instance, potentially leading to further compromise of the hosting environment or connected systems.

Defenders should treat this as a high-priority issue for any organization running the listed Sitecore products. Confirm all technical details, affected configurations, and remediation steps against the official vendor advisory, as public information remains limited to the high-level description provided by CISA.

How it works

The underlying weakness is CWE-502: deserialization of untrusted data. In ASP.NET applications such as Sitecore, machine keys are used to protect and validate serialized data (for example, ViewState or authentication tickets). When default or otherwise predictable machine keys are present and exposed, an attacker who can supply crafted serialized input may cause the application to deserialize malicious objects.

Deserialization of untrusted data can result in arbitrary code execution because the deserialization process can instantiate and invoke attacker-controlled types. In this case the CISA summary states that the flaw allows remote code execution via exploitation of those exposed ASP.NET machine keys. Exact payload formats, entry points, or required network access conditions are not detailed in the available facts and must be verified against the vendor advisory.

Am I affected? How to find it in your systems

The vulnerability affects Sitecore Experience Manager (XM), Experience Platform (XP), Experience Commerce (XC), and Managed Cloud deployments. These products commonly run as web applications on Windows servers or in cloud-hosted environments that use ASP.NET.

• Inventory all Sitecore instances by searching configuration management databases, cloud asset inventories, and web-server directories for Sitecore-related binaries, configuration files, or service names.
• Examine machine-key settings in web.config or equivalent configuration stores; look for the presence of default or well-known ASP.NET machine keys rather than uniquely generated values.
• Review application and IIS logs for anomalous POST requests that contain large or unusual ViewState, authentication, or other serialized payloads, especially those that produce unexpected errors or process creation events.
• Check for unexpected child processes spawned by the Sitecore application pool identity, which can be a post-exploitation indicator of successful code execution.

Because exact version ranges and configuration prerequisites are not supplied in the available facts, treat every installation of the listed products as potentially affected until the vendor advisory is consulted.

How to remediate

The primary remediation is to apply the mitigations or updates published by Sitecore, following the vendor’s instructions exactly. CISA’s required action is to apply those mitigations, follow applicable BOD 22-01 guidance for any cloud-hosted instances, or discontinue use of the product if mitigations are unavailable.

• Obtain the official Sitecore advisory and apply the recommended patches or configuration changes without delay.
• After patching, regenerate and replace any default or previously exposed machine keys with strong, unique values.
• Restart application pools and verify that the new machine-key configuration is active.
• For Managed Cloud or other hosted offerings, coordinate with the service provider to confirm that the vendor-supplied mitigations have been applied.

Document the change and re-scan the environment to confirm that default machine keys are no longer present.

If you can't patch immediately

Until the vendor update can be applied, reduce exposure with compensating controls appropriate to a deserialization-to-RCE weakness:

• Segment Sitecore servers so they are reachable only from trusted management and application tiers; block unnecessary inbound access from the internet or untrusted networks.
• Deploy virtual patching or WAF rules that inspect and block requests containing suspicious serialized data patterns commonly associated with ASP.NET ViewState or similar constructs (confirm rule efficacy against the vendor’s guidance).
• Disable any non-essential features or endpoints that accept serialized input if the vendor documentation indicates they can be safely turned off.
• Increase monitoring of the Sitecore application pool for anomalous process creation, outbound network connections, and file-system modifications; alert on any such activity.
• For cloud deployments, follow BOD 22-01 practices such as restricting public exposure and enabling enhanced logging.

These measures lower risk but do not eliminate it; schedule the permanent vendor remediation as soon as possible.

If your data may have been exposed

Vulnerabilities that enable remote code execution can be used to steal data, install persistence, or move laterally. Although ransomware use is not documented for this CVE, any successful exploitation should be treated as a potential breach. Review Sitecore and supporting system logs for indicators of compromise, rotate credentials that may have been accessible to the application, and examine connected data stores for unauthorized access. Organizations can also run a free exposure scan of their email addresses against known breach data sets to determine whether related credentials have appeared in prior incidents.