Sitecore ViewState Deserialization RCE via Exposed Sample machineKey
CVE-2025-53690 is a critical deserialization of untrusted data vulnerability in Sitecore Experience Manager (XM) and Sitecore Experience Platform (XP) through version 9.0. The issue is described as a ViewState deserialization flaw in ASP.NET handling within Sitecore deployments that reused a publicly exposed sample machineKey from older Sitecore deployment guidance. Because the machineKey is used to validate and protect ViewState, an attacker who knows the reused sample key can forge a malicious ViewState payload that the server accepts as legitimate. The supplied content also indicates exploitation against endpoints such as /sitecore/blocked.aspx using crafted HTTP POST requests containing malicious ViewState data. Successful deserialization of attacker-controlled .NET objects can result in arbitrary code execution in the Sitecore application context, commonly noted as the IIS application pool / NETWORK SERVICE context. The vulnerability has been reported as actively exploited in the wild.
Are you exposed to this one?
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
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
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
118 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.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.