⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Critical · CVSS 9.3 ⚠ ACTIVELY EXPLOITED — CISA KEV

How to Fix CVE-2025-22224: Out-of-Bounds Write in ESXi

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 9.3 - Critical
Actively exploited?Yes, listed in CISA KEV (added 2025-03-04)
Affected8.0 < ESXi80U3d-24585383, 8.0 < ESXi80U2d-24585300, 7.0 < ESXi70U3s-24585291, 17.x < 17.6.3, 5.x, 4.5.x, 5.x, 4.x, 3.x, 2.x, and others
Fixed inSee vendor advisory
Type (CWE)Not verified
Patch immediately. CISA's KEV listing means active exploitation is confirmed. Federal agencies must remediate by 2025-03-25.

What is CVE-2025-22224?

CVE-2025-22224 is an out-of-bounds write flaw in ESXi. Malformed input causes a write past the intended buffer boundary, which leads to memory corruption and remote code execution in observed exploits. Vendor description: VMware ESXi, and Workstation contain a TOCTOU (Time-of-Check Time-of-Use) vulnerability that leads to an out-of-bounds write. A malicious actor with local administrative privileges on a virtual machine may exploit this issue to execute code as the virtual machine's VMX process running on the host.

Why this CVE matters

Out-of-bounds writes in a parsing path are a reliable building block for remote code execution. The attacker only needs to send a crafted message, which makes mass scanning trivial once a working exploit lands in public tooling.

For deployments of ESXi 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:

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.

On VMware ESXi, run vmware -vl to read the build number. On vCenter, the version is shown on the login banner and in the admin UI under the Help menu.

How to fix CVE-2025-22224

  1. Read the vendor advisory in full: https://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/25390
  2. Upgrade ESXi to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. 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://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/25390
# Debian / Ubuntu
sudo apt update
sudo apt install --only-upgrade esxi

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

# openSUSE
sudo zypper update esxi

# Verify the running version matches the fixed version
dpkg -s esxi 2>/dev/null | grep -i version || rpm -q esxi 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://support.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvisories/0/25390
#    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-2025-22224 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

Block network reachability to the vulnerable service from untrusted networks and apply the patched build. Memory-corruption bugs cannot be reliably mitigated at the network layer; the patch is the fix.

How to verify the fix worked

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 repeated service restarts, crash logs from the affected daemon, and core files generated around the time of any anomalous traffic. A memory-corruption flaw used for exploitation often leaves a trail of failed attempts before the successful one. Because ESXi 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-2025-22224 being exploited in the wild?

Yes. CISA added CVE-2025-22224 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-2025-22224?

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.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for ESXi run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*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.*