Threats / Microsoft / CVE-2021-31196
CVE-2021-31196
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Microsoft Exchange Server vulnerability
Microsoft Exchange Server information disclosure vulnerability enabling remote code execution. Exploited in the wild with low EPSS score.
Verdict
Today item — known-exploited.
An information disclosure flaw in Microsoft Exchange Server permits remote code execution. Active exploitation observed in the wild, though predicted exploitation likelihood remains low. Patch availability recommended for affected deployments.
CISA KEV Yes · 2024-08-215EPSS 0.54056 (verify live)6CVSS 7.23CISA SSVC Exploitation: active · Automatable: yes · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreReported 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 2024-08-21).
Probability (EPSS)
EPSS 0.54056 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.2 (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C) · Affected: Microsoft, Exchange Server. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 1134 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
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 discover or obtain information about Exchange Server configuration, credentials, or internal paths through the disclosure vulnerability.
Business
Sensitive organizational data and system architecture details are exposed to threat actors.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I leverage the disclosed information to craft and deliver a remote code execution payload to the vulnerable Exchange Server.
Business
Attackers gain arbitrary code execution within the email infrastructure, a critical trust boundary.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistence and lateral movement from the compromised Exchange Server into the broader network.
Business
Email systems become a beachhead for enterprise-wide compromise, affecting business continuity and data security.
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’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by microsoftCNA
Credited with finding itOrange Tsai (@orange_8361) with DEVCOREfinder
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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