How to Fix CVE-2025-53690: Deserialization RCE in Experience Manager (XM)

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*By Sai Kiran Pandrala*

Patch immediately. CISA's KEV listing means active exploitation is confirmed. Federal agencies must remediate by 2025-09-25.

What is CVE-2025-53690?

CVE-2025-53690 is an unsafe deserialization in Experience Manager (XM). The application accepts attacker-controlled serialized objects and reconstructs them without validating their type, so a crafted payload triggers code execution inside the running process. Unauthenticated remote code execution is the typical impact. Vendor 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.

Why this CVE matters

Deserialization bugs are a favorite of ransomware operators because they convert a single HTTP request into full code execution on the target host. Public proof-of-concept code for this CVE class typically appears within days of disclosure, and weaponized exploits follow shortly after.

For deployments of Experience Manager (XM) that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Confirmed in-the-wild exploitation makes that assumption mandatory, not cautious. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

• Experience Manager (XM): 0 <= 9.0
• Experience Manager (XM): 0 <= 9.0

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open Experience Manager (XM)'s About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2025-53690

1. Read the vendor advisory in full: https://cloud.google.com/blog/topics/threat-intelligence/viewstate-deserialization-zero-day-vulnerability
2. Upgrade Experience Manager (XM) to the patched build listed in the vendor advisory.
3. Back up the configuration (and database, where applicable) before upgrading.
4. Rotate any credentials, API keys, or session tokens that the vulnerable service touched. An unauthenticated RCE-class flaw means anything the process could see should be treated as exposed.
5. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
6. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Patch via your OS package manager

# The exact package name and patched version are listed in the vendor advisory:
# https://cloud.google.com/blog/topics/threat-intelligence/viewstate-deserialization-zero-day-vulnerability
# Debian / Ubuntu
sudo apt update
sudo apt install --only-upgrade experiencemanagerxm

# RHEL / Rocky / AlmaLinux / Fedora
sudo dnf upgrade experiencemanagerxm

# openSUSE
sudo zypper update experiencemanagerxm

# Verify the running version matches the fixed version
dpkg -s experiencemanagerxm 2>/dev/null | grep -i version || rpm -q experiencemanagerxm 2>/dev/null

# Windows: pull the cumulative update that ships this fix.
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck
Get-WindowsUpdate -AcceptAll -Install -AutoReboot

Verify the fix landed

# 1. Confirm the running version matches the fixed-in version from the advisory:
#    https://cloud.google.com/blog/topics/threat-intelligence/viewstate-deserialization-zero-day-vulnerability
#    Use the platform-specific version probe above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag CVE-2025-53690 on the patched target.

# 3. Inspect recent service / kernel logs for crash loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

If you cannot patch immediately

There is no safe runtime mitigation for deserialization flaws beyond removing exposure: block the affected endpoint at a reverse proxy or WAF and restrict access to authenticated, trusted users only. Patch as soon as possible.

How to verify the fix worked

• After applying the patch, verify the running version in the product's admin UI or via the vendor-documented CLI command.
• Confirm the patched build matches the version listed in the vendor advisory.
• Run an authenticated vulnerability scan with a current signature set and confirm the scanner no longer flags CVE-2025-53690.
• Review logs for the entire pre-patch window for indicators of compromise listed in the vendor or CISA advisory.
• Confirm any network-layer mitigations that were applied as a stopgap have been reverted (or left in place intentionally) once the patch is verified.

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in Experience Manager (XM), scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation. Because Experience Manager (XM) sits on CISA's Known Exploited Vulnerabilities catalog for this CVE, defenders should also pull the IOC list from the vendor advisory and from CISA's analysis if one was published.

Frequently asked questions

Is CVE-2025-53690 being exploited in the wild?

Yes. CISA added CVE-2025-53690 to the Known Exploited Vulnerabilities catalog, which means active exploitation has been confirmed by federal observation or credible vendor reporting.

Will a WAF or IDS rule fully mitigate CVE-2025-53690?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

Do I need to assume compromise if my Experience Manager (XM) was internet-facing and unpatched?

For an unauthenticated RCE-class flaw exposed to the public internet during the known exploitation window, yes. Review logs, rotate credentials the process could access, and look for unexpected accounts, scheduled tasks, or outbound connections.

References

• Official vendor advisory: https://cloud.google.com/blog/topics/threat-intelligence/viewstate-deserialization-zero-day-vulnerability
• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2025-53690
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• Additional vendor or research reference: https://support.sitecore.com/kb?id=kb_article_view&sysparm_article=KB1003865
• Additional vendor or research reference: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-53690

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*