Sitecore ViewState deserialization RCE via exposed sample machineKey
CVE-2025-53690 is a deserialization of untrusted data vulnerability affecting Sitecore Experience Manager (XM) and Sitecore Experience Platform (XP) through version 9.0. Multiple supporting reports describe the flaw as an ASP.NET ViewState deserialization issue in certain Sitecore deployments that reused a publicly exposed sample/default machineKey from Sitecore deployment guidance published in or before 2017. When a vulnerable deployment uses that known machineKey, an attacker can forge a malicious ViewState payload that the server accepts as valid and deserializes, resulting in code injection / remote code execution. Reporting also indicates exploitation against public-facing Sitecore endpoints such as /sitecore/blocked.aspx using crafted HTTP POST requests containing malicious ViewState data. Successful execution has been reported to occur pre-authentication on internet-facing deployments, typically in the IIS worker context (reported as NETWORK SERVICE in some analyses).
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Impact, mitigation & remediation
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Impact
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Exploits
No valid public exploits. Mallory filtered out 3 candidates as fakes, detection scripts, or README-only repos.
All candidate exploits were filtered out by Mallory's validation.
Affected products & vendors
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Recent activity
116 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A critical Sitecore vulnerability that CISA reports is under active exploitation in the wild.
A critical Sitecore ASP.NET ViewState insecure deserialization issue caused by default/sample ASP.NET machineKey values, enabling attackers to forge ViewState payloads, bypass authentication, and achieve remote code execution (RCE) (noted as running under IIS NETWORK SERVICE).
A zero-day ViewState deserialization vulnerability affecting SiteCore products, reportedly exploited in recent activity and associated with UAT-8837 infrastructure and TTPs.
A critical zero-day vulnerability in Sitecore reportedly used for initial access by the Chinese state-sponsored operation UAT-8837 against North American critical infrastructure entities.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.