basicsecurity.net
Proof, not just disclosure.
Threats / Microsoft / CVE-2021-27059
CVE-2021-27059 · EUVD no mirror located · GCVE no mirror located Verified 2026-06-22

Microsoft Office vulnerability

Microsoft Office contains an unspecified remote code execution vulnerability that has been exploited in the wild.

Verdict

Today item — known-exploited.

This vulnerability enables unauthenticated remote code execution through Microsoft Office, likely via malicious document delivery. Active exploitation in the wild indicates immediate risk to organizations using affected Office versions.

CISA KEV Yes · 2021-11-033EPSS 0.03182 (verify live)4
01

Is it exploitable?

— the evidence, ranked above the score
Reported exploitation
3 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).
CISA KEV ↗Confirmed
Probability (EPSS)
EPSS 0.03182 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Office. Confirm exact fixed builds in the vendor advisory.
NVD ↗Reported
02

Who’s exploiting it?

— attribution turns risk into urgency
Attribution 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 board
1

Front door — unauthenticated access narrative 1

Attacker
Craft a malicious Office document and distribute it via email or web to target users.
Business
Users open documents containing embedded exploit code, leading to unauthorized code execution on endpoints.
2

Keys to the kingdom — privilege/identity takeover narrative 2

Attacker
Execute arbitrary commands with the privileges of the Office application process.
Business
Attackers gain initial access to corporate networks and can move laterally to sensitive systems.
3

Lateral reach — past segmentation narrative 3

Attacker
Establish persistence and exfiltrate data or deploy secondary payloads.
Business
Data breaches, intellectual property theft, and operational disruption across affected organizations.
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

Coverage & confidence

— what we know, and what we don’t

Established (cited)

  • KEV listing (CISA)
  • EPSS probability (FIRST)
  • 3 reported-exploitation source(s)
  • Catalogued by microsoft (CNA)
  • Coverage gaps — stated, not hidden

  • No EUVD / GCVE mirror in feed — single-authority dependency for the identifier.
  • EPSS & exposure are time-varying; verify live at the source.
  • Threat-actor attribution not established from feed data — absence of a name is not absence of compromise.
  • No finder/reporter credit recorded in the public CVE entry — the work behind this find is unattributed.
  • Disclosure & credit2
    Catalogued by microsoftCNA
    Credited with finding itNo finder named in the public CVE record — the work behind this find is unattributed.