CyberSecBulletin
CVE-2025-41236NVD status: Deferred

ESXi: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2025-41236 is a critical-severity out-of-bounds write vulnerability in ESXi from VMware, with a CVSS 3.1 base score of 9.3 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions ESXi80U3f-24784735, ESXi80U2e-24789317, ESXi70U3w-24784741 as the first without the flaw, so updating ESXi to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 2.63% chance of exploitation within 30 days, higher than 86% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update ESXi to ESXi80U3f-24784735 or ESXi80U2e-24789317 or ESXi70U3w-24784741, whichever matches your release line, or a later version.
  2. Update Workstation to 17.6.4 or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
VMwareESXi8.0 up to, but not including, ESXi80U3f-24784735; 8.0 up to, but not including, ESXi80U2e-24789317; 7.0 up to, but not including, ESXi70U3w-24784741ESXi80U3f-24784735, ESXi80U2e-24789317, ESXi70U3w-24784741
VMwareCloud Foundation5.x, 4.5.xNot stated
VMwareWorkstation17.x up to, but not including, 17.6.417.6.4
VMwareFusion13.x through 13.6.4Not stated
VMwareTelco Cloud Platform5.x, 4.x, 3.x, 2.xNot stated
VMwareTelco Cloud Infrastructure3.x, 2.xNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (vmware.com).

Official description

VMware ESXi, Workstation, and Fusion contain an integer-overflow vulnerability in the VMXNET3 virtual network adapter. A malicious actor with local administrative privileges on a virtual machine with VMXNET3 virtual network adapter may exploit this issue to execute code on the host. Non VMXNET3 virtual adapters are not affected by this issue.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in ESXi

All ESXi vulnerabilities

Recent Out-of-bounds Write vulnerabilities

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