Vulnerability report

Trusted Third Party Report Confirmed Confidence In CISA KEV

CVE-2021-31196

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server 2013 Cumulative Update 23 · affected before 15.00.1497.023

Watch CVE-2021-31196 Browse KEV feed
Severity
CVSS 7.2 · High
Confidence
Confirmed
Exploit status
Trusted Third Party Report
EPSS
54.1%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-31196 is Microsoft Exchange Server Remote Code Execution Vulnerability.

Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Who is affected?

Affected products include Microsoft Exchange Server 2013 Cumulative Update 23 and 4 other products, including affected before 15.00.1497.023, affected before 15.01.2242.012, and affected before 15.01.2308.014.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Affected
Microsoft Exchange Server 2013 Cumulative Update 23
Before 15.00.1497.023
Microsoft Affected
Microsoft Exchange Server 2016 Cumulative Update 20
Before 15.01.2242.012
Microsoft Affected
Microsoft Exchange Server 2016 Cumulative Update 21
Before 15.01.2308.014
Microsoft Affected
Microsoft Exchange Server 2019 Cumulative Update 10
Before 15.02.0922.013
Microsoft Affected
Microsoft Exchange Server 2019 Cumulative Update 9
Before 15.02.0858.015
View vendor advisory (opens in new tab)
Published
14 Jul 2021
Exploitation Attempts Reported
21 Aug 2024
Attack vector
Remote
Complexity
Low
Privileges
High
User interaction
None

Tags

cisa microsoft nessus_scanner

CVE References

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation Attempts Observed in the Wild

CISA

Recorded 21 Aug 2024

A trusted third party reported exploitation attempts.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CISA First 2024-08-21 00:00 UTC
CVE 2026-08-10 15:30 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nessus https://www.tenable.com/plugins/nessus/151664 02 Jun 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

7.2 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

EPSS

54.1%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

All CVSS Scores

CVSS v3.1 7.2 High

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS v2.0 6.5 Medium

AV:N/AC:L/Au:S/C:P/I:P/A:P

Timeline

From disclosure to observed exploitation attempts

  1. 15:30 UTC

    KEV confirmed by CVE

    Exploitation attempts reported by an external source

  2. 09:26 UTC

    Nessus plugin available

    Scanner coverage available

  3. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. 17:53 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-31196

Sample API response 
{
  "cve_id": "CVE-2021-31196",
  "confidence": "Confirmed",
  "cvss_score": 7.2,
  "cvss_estimated": false,
  "epss_score": 0.54056,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}