Threats / Microsoft / CVE-2025-21335
CVE-2025-21335
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Microsoft Windows vulnerability
A use-after-free vulnerability in Windows Hyper-V NT Kernel Integration VSP allows local attackers to escalate privileges to SYSTEM level.
Verdict
Today item — known-exploited.
Local privilege escalation via memory safety defect in Hyper-V kernel component. Exploitation requires local access but yields highest system privilege, enabling full system compromise.
CISA KEV Yes · 2025-01-145EPSS 0.01363 (verify live)6CVSS 7.83CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
6 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-01-14).
Probability (EPSS)
EPSS 0.01363 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C) · Affected: Microsoft, Windows. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-416 Use After Free — weakness family: Memory safety.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog the same day the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I gain initial local access to a Windows system running Hyper-V.
Business
An insider, contractor, or compromised user account exists on the network.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I trigger the use-after-free condition in the Hyper-V NT Kernel Integration VSP component through crafted local operations.
Business
The vulnerability is reachable without special configuration or additional exploits.
3
Lateral reach — past segmentation narrative 3
Attacker
I execute arbitrary code with SYSTEM privileges by exploiting the freed memory reference.
Business
The attacker gains unrestricted control over the entire host system and all hosted virtual machines.
4
Data at risk — exfiltration narrative 4
Attacker
I persist access, disable security controls, and move laterally across the infrastructure.
Business
Containment fails; the compromise spreads to dependent systems, data stores, and connected networks.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05