Threats / Microsoft / CVE-2021-28310
CVE-2021-28310
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft Win32k vulnerability
Microsoft Win32k contains an out-of-bounds write vulnerability enabling local privilege escalation. The flaw has been exploited in active attacks.
Verdict
Today item — known-exploited.
A local attacker can write to arbitrary memory locations in Win32k to escalate privileges on affected Windows systems. Active exploitation in the wild demonstrates practical attack viability.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
8 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 2021-11-03).
Probability (EPSS)
EPSS 0.0833 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Win32k. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-787 Out-of-bounds Write — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
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 craft a malicious application that triggers the out-of-bounds write in Win32k through a crafted system call.
Business
An unprivileged user account becomes compromised with system-level access, bypassing security boundaries.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the elevated privileges to install persistent malware or access sensitive system resources.
Business
Attackers gain durable foothold for lateral movement, data exfiltration, or further system compromise.
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