CVE-2021-1647

Microsoft Defender: Remote Code Execution

As of , CVE-2021-1647 in Microsoft Defender is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch soon.

Exploited
Yes: CISA listed it on 3 November 2021
US federal deadline
17 November 202114 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
EPSS score
0.39Higher than 98% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
EPSS when listed
Not availableCISA listed it before 4 February 2022, where the EPSS files we read begin.
Public exploit
None foundNeither Metasploit nor Exploit-DB lists one.
Fix
No vendor link in CISA's entry

What CISA says to do

Apply updates per vendor instructions.

CISA's required action

What the flaw is

Microsoft Defender contains an unspecified vulnerability that allows for remote code execution.

CISA's description

Microsoft Defender Remote Code Execution Vulnerability

The CVE record's description, from microsoft

CVE published
12 January 2021
Assigned by
microsoft
CVSS
7.8 High (CVSS 3.1, from the CNA)
CWE-122
Heap-based Buffer Overflow
CWE-1285
Improper Validation of Specified Index, Position, or Offset in Input
CISA SSVC, exploitation
active
CISA SSVC, automatable
no
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Defender: other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2026-33825Insufficient Granularity of Access ControlMicrosoft DefenderPatch nowRansomware use, listed within a year0.00
CVE-2022-44698SmartScreen Security Feature BypassMicrosoft DefenderPatch this weekRansomware use; EPSS 0.760.76
CVE-2026-45498Denial of ServiceMicrosoft DefenderPatch soon0.01
CVE-2026-41091Link FollowingMicrosoft DefenderPatch soon0.00

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