CVE-2025-27218 Overview
CVE-2025-27218 affects Sitecore Experience Manager (XM) and Experience Platform (XP) version 10.4 prior to KB1002844. The vulnerability stems from insecure deserialization of untrusted data, which allows remote code execution against affected Sitecore instances. The flaw maps to CWE-94: Improper Control of Generation of Code. Sitecore published remediation guidance in knowledge base article KB1003535. The EPSS score of 75.678% (98.926 percentile) indicates a high likelihood of exploitation activity relative to other published CVEs.
Critical Impact
Unauthenticated attackers can deliver crafted serialized payloads over the network to execute arbitrary code on vulnerable Sitecore XM and XP 10.4 servers.
Affected Products
- Sitecore Experience Manager (XM) 10.4 before KB1002844
- Sitecore Experience Platform (XP) 10.4 before KB1002844
- Sitecore deployments that have not applied the KB1003535 guidance
Discovery Timeline
- 2025-02-20 - CVE-2025-27218 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-27218
Vulnerability Analysis
The vulnerability is an insecure deserialization issue in Sitecore XM and XP 10.4. The platform deserializes attacker-controlled input without validating the type or contents of the serialized object graph. An attacker who can reach an exposed Sitecore endpoint can submit a crafted serialized payload that triggers gadget chains during object reconstruction. Successful exploitation leads to remote code execution in the context of the Sitecore application process.
The issue is reachable over the network and requires no authentication or user interaction. It is classified under CWE-94: Improper Control of Generation of Code, reflecting the platform's handling of attacker-supplied data as executable logic during deserialization. Public exploit material is referenced in Exploit-DB, increasing operational risk for unpatched deployments.
Root Cause
The root cause is the use of an unsafe deserializer that accepts arbitrary serialized .NET object types without type filtering or allow-lists. When the application reconstructs objects from request data, gadget classes available in the runtime can chain side effects that culminate in command execution. The fix shipped in KB1002844 restricts the types permitted during deserialization.
Attack Vector
An attacker sends an HTTP request containing a crafted serialized payload to a vulnerable Sitecore XM or XP 10.4 endpoint. Because the attack vector is network-based and no privileges or user interaction are required, automated scanning and mass exploitation are practical once a working gadget chain is published. Technical details and the official fix are described in the Sitecore Knowledge Base Article.
Detection Methods for CVE-2025-27218
Indicators of Compromise
- HTTP requests to Sitecore endpoints containing Base64-encoded .NETBinaryFormatter or LosFormatter payloads.
- Unexpected child processes spawned from the Sitecore IIS worker process w3wp.exe, such as cmd.exe, powershell.exe, or rundll32.exe.
- New or modified .aspx, .ashx, or .asmx files in Sitecore web roots that were not introduced by deployment pipelines.
- Outbound connections from Sitecore servers to unfamiliar hosts shortly after inbound POST requests with large serialized bodies.
Detection Strategies
- Inspect IIS and Sitecore application logs for anomalous POST requests with large request bodies targeting administrative or pipeline endpoints.
- Monitor process lineage on Sitecore servers and alert when w3wp.exe spawns interpreters or LOLBins.
- Apply web application firewall rules that flag serialized object signatures such as AAEAAAD///// in request bodies.
Monitoring Recommendations
- Forward IIS, Windows Security, and Sitecore logs to a centralized analytics platform for correlation across hosts.
- Baseline normal Sitecore outbound traffic and alert on deviations, particularly to internet-facing destinations.
- Track file integrity in Sitecore web roots and configuration directories to detect post-exploitation webshells.
How to Mitigate CVE-2025-27218
Immediate Actions Required
- Apply the Sitecore-supplied hotfix referenced in KB1002844 to all Sitecore XM and XP 10.4 instances.
- Restrict network exposure of Sitecore administrative and content-management endpoints to trusted networks or VPNs.
- Audit Sitecore servers for indicators of prior exploitation, including unexpected files, scheduled tasks, and service accounts.
Patch Information
Sitecore addresses the deserialization flaw in the update described in the Sitecore Knowledge Base Article KB1003535, which references hotfix KB1002844. Administrators should review the article for version-specific deployment steps and verify the fix in non-production environments before rolling out to production.
Workarounds
- Place Sitecore content-management endpoints behind a web application firewall configured to block serialized .NET payload signatures.
- Limit access to Sitecore management interfaces using IP allow-lists at the load balancer or reverse proxy.
- Run the Sitecore application pool under a least-privilege service account to reduce the impact of code execution.
# Example IIS request filtering to block oversized request bodies on management paths
appcmd set config "Default Web Site/sitecore" -section:requestFiltering /requestLimits.maxAllowedContentLength:1048576
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
