Vulnerability

CVE-2021-31207

Medium· 6.6KEVEXPLOITCVSS6.6EPSS94%

.rules3/5

Microsoft Exchange Server Security Feature Bypass Vulnerability

Microsoft Exchange Server contains an unspecified vulnerability that allows for security feature bypass.

Threat signal

96/100

Severe

Severity

medium

CVSS

6.6

EPSS

94%

Active

KEV

CISA KEV — actively exploited

Ransomware: Known1669d overdue

AffectedMicrosoft — Exchange Server

Added to KEV

2021-11-03

Federal patch due (BOD 22-01)

2021-11-17

Required action (CISA verbatim)

Apply updates per vendor instructions.

Vendor advisory + references

https://nvd.nist.gov/vuln/detail/CVE-2021-31207

CISA description: “Microsoft Exchange Server contains an unspecified vulnerability that allows for security feature bypass.”

CVSS

v3.1Open in FIRST calculator →

6.6/ 10MEDIUMCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityHighRequires conditions outside attacker's control (race, brute-force, configuration
Privileges RequiredHighAdmin / root privileges required.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactHighTotal compromise of integrity — full data modification possible.
Availability ImpactHighTotal loss of availability — full DoS possible.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

93.8%

probability of exploitation in next 30 days

p100

higher than 100% of all CVEs

3-day trend↑ 0pp

Statistically about to be weaponized — top-tier triage urgency.

Vendor VEX

No VEX statements published for CVE-2021-31207. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCAttend

Active exploitation with limited impact — coordinate patching

exploitation: active
automatable: no
impact: partial
mission: support

Lifecycle

2021-11-03Added to CISA KEVransomware: Known
2021-11-03Public exploit observedmetasploit
2021-11-03Published
2021-11-17Federal patch due (BOD 22-01)
2026-06-12Last modified1 source

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.