CriticalCVE-2025-53690

    Sitecore Products ViewState Deserialization Vulnerability (CVE-2025-53690)

    Published Last modified In CISA KEV since Sources: pwn.watch, CVE.org

    What is affected, what to do

    This vulnerability allows remote code execution (RCE) through deserialization of untrusted data in Sitecore Experience Manager (XM), Experience Platform (XP), and Experience Commerce (XC) due to default machine keys. An attacker can exploit exposed ASP.NET machine keys to gain full control over the affected systems. The vulnerability is actively exploited in the wild and has been observed in ransomware campaigns since September 2025. All versions up to and including 9.0 of the affected products are at risk. Immediate patching to the latest available version is critical to mitigate the risk of exploitation.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Sitecore Experience Manager (XM) lte *..9.0
    • Sitecore Experience Platform (XP) lte *..9.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.0

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.0

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, CVE.org

    60.6 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.14

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    234.35 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.0 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    60.6 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.14
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 5 September 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-502

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication. The nominally high attack complexity collapses wherever the sample machine key is in use, because the key is public. In that case a crafted ViewState payload gives direct code execution in the IIS worker context, with impact beyond the application itself. Exploitation likelihood is very high, placing this among the CVEs most likely to be exploited. CISA does not flag known ransomware use, but observed intrusions involved reconnaissance, account creation and lateral movement after initial access — classic staging for follow-on operations. Treat internet-facing Sitecore instances with unverified key provenance as critical and act now. Internal-only instances with demonstrably unique keys can follow the normal patch cycle.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory every Sitecore instance (XM, XP, XC, Managed Cloud) and inspect the <machineKey> element in each web.config. Any deployment whose validationKey/decryptionKey was copied from the sample keys published in Sitecore's deployment guides is exploitable. The "9.0" version scope is only a pointer: newer versions are also at risk if the key was carried over from older installs.
      • Preserve evidence before remediating: collect IIS logs, Windows Application/Security/Sysmon logs and a filesystem snapshot of the webroot. Rotating keys does not remove persistence an attacker may already have established (webshells, created accounts, tunnelling tools).
      • Rotate machine keys immediately: generate unique random keys per instance, for example via IIS Manager → "Machine Key" → "Generate Keys" or PowerShell with RNGCryptoServiceProvider. Then recycle the app pool. In farms, update all nodes of a role consistently.
      • Apply Sitecore's security guidance for CVE-2025-53690. A patch and hardening guidance are available from the vendor — look up the exact version in the vendor advisory. For Managed Cloud, get explicit confirmation of remediation status from Sitecore support.
      • If indicators of compromise are present, isolate the host. Rotate every credential reachable from the server: SQL connection strings, service accounts, xConnect certificates, API keys. Only then rebuild or return the host to production.

    2. Runbook step 2

      Mitigation layers

      • Configuration: encrypt the <machineKey> section with aspnet_regiis -pe "system.web/machineKey". Confirm enableViewStateMac has not been disabled. Never store keys in repos, images or templates, and scan CI/CD artefacts for inherited legacy keys.
      • Network segmentation: keep CM/authoring servers (/sitecore/*) off the internet and reachable only via VPN or ZTNA. Place CD servers in a DMZ with an egress allowlist limited to database, Solr and xConnect. This breaks reverse shells and tunnels.
      • WAF/IPS: block or alert on POST requests carrying a __VIEWSTATE parameter to public CD endpoints that need no WebForms postback, particularly default Sitecore pages such as /sitecore/blocked.aspx. Also flag oversized ViewState values (e.g. >2 KB) sent to non-interactive pages.
      • Endpoint hardening: use EDR or ASR rules to prevent w3wp.exe from spawning cmd.exe, powershell.exe, whoami.exe or net.exe. Run app pools under least-privilege identities, never LocalSystem.
      • IAM/least privilege: Sitecore server accounts must not hold domain-admin or broadly shared service rights. Monitor local Administrators group membership on web servers and manage local admin passwords with LAPS.

    3. Runbook step 3

      Detection rules

      • ASP.NET event log: Windows Application log, Event ID 1316 (event code 4009, "Viewstate verification failed"). Bursts indicate key guessing. A successful exploit with the correct key logs no error, so correlate with process telemetry.
      • EDR/Sysmon EID 1: process ancestry w3wp.exe → cmd.exe/powershell.exe/csc.exe/whoami.exe/nltest.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "w3wp.exe" and FileName in~ ("cmd.exe","powershell.exe","whoami.exe","net.exe","nltest.exe","csc.exe")
      • IIS access logs: cs-method=POST with __VIEWSTATE to .aspx pages normally only fetched via GET, such as /sitecore/blocked.aspx. Also look for requests from unfamiliar IPs returning HTTP 200 with an unusual response size. SPL: index=iis cs_method=POST cs_uri_stem="/sitecore/*.aspx" | stats count by c_ip, cs_uri_stem
      • Persistence and lateral movement: Sysmon EID 11 for new .aspx, .ashx or .dll files in the webroot or \bin. Security log 4720/4732 for new local accounts or admin group additions on Sitecore hosts. 4624 logon type 10 (RDP) originating from web servers.
      • Network (Zeek/Suricata): outbound connections from Sitecore servers to unknown internet destinations, especially long-lived TLS or SOCKS tunnels. Also internal SMB/RDP scanning originating from the DMZ.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Deserialization of Untrusted Data vulnerability in Sitecore Experience Manager (XM), Sitecore Experience Platform (XP) allows Code Injection.This issue affects Experience Manager (XM): through 9.0; Experience Platform (XP): through 9.0.

    Source: pwn.watch, cvelistv5, NVD (NIST), CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    SitecoreExperience Manager (XM)
    • ≤ 9.0
    • —
    SitecoreExperience Platform (XP)
    • ≤ 9.0
    • —
    sitecoreexperience_commerce
    • ≤ 9.0
    • —
    sitecoreexperience_manager
    • ≤ 9.0
    • —
    sitecoreexperience_platform
    • ≤ 9.0
    • —
    sitecoremanaged_cloud
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-502Deserialization of Untrusted Data

      Base

      The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

      Entry at MITRE CWE-502

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • cloud.google.comblog/topics/threat-intelligence/viewstate-deserialization-zero-…Exploit, Third-party advisory
    • support.sitecore.comSitecore advisory: Sitecore Multiple ProductsVendor advisory, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53690government-resource, US government resource
    • pwn.watchpwn.watch: Sitecore Multiple Products: Multiple Products Deserialization of Untrusted Data Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2025-53690pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    One NVD translation into another language is hidden.

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