basicsecurity.net
Proof, not just disclosure.
Threats / Microsoft / CVE-2020-1147
CVE-2020-1147 · EUVD no mirror located · GCVE no mirror located Verified 2026-06-22

Microsoft .NET Framework, SharePoint, Visual Studio vulnerability

Microsoft .NET Framework, SharePoint, and Visual Studio contain an XML deserialization remote code execution vulnerability that fails to validate source markup, allowing attackers to execute arbitrary code in the deserialization process con

Verdict

Today item — known-exploited.

This vulnerability enables unauthenticated remote code execution through malicious XML input. The high EPSS score and confirmed wild exploitation indicate active abuse. Organizations must prioritize patching affected Microsoft products immediately.

CISA KEV Yes · 2021-11-033EPSS 0.94243 (verify live)4
01

Is it exploitable?

— the evidence, ranked above the score
Reported exploitation
1 independent public report of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
cisa.gov ↗Confirmed
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
CISA KEV ↗Confirmed
Probability (EPSS)
EPSS 0.94243 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, .NET Framework, SharePoint, Visual Studio. 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
I craft malicious XML content designed to exploit unsafe deserialization in the target application.
Business
Attackers gain code execution within the application process, enabling full system compromise and data exfiltration.
2

Keys to the kingdom — privilege/identity takeover narrative 2

Attacker
I deliver the XML payload through application input vectors such as file uploads, web requests, or document processing.
Business
The organization loses control of affected servers and workstations, with potential lateral movement across the network.
3

Lateral reach — past segmentation narrative 3

Attacker
I establish persistence and escalate privileges to maintain long-term access to compromised infrastructure.
Business
Incident response costs, operational downtime, and regulatory penalties accumulate as the breach scope expands.
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)
  • 1 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.