CVE-2021-31196 | Microsoft Exchange Server Remote Code Execution Vulnerability

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Microsoft Exchange Server Remote Code Execution Vulnerability

Published: 2021-07-14 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-31196 is rated Critical Active Threat (93.3/100): CVSS High severity, with high exploitation likelihood (EPSS 46.38%, 99th percentile). CISA KEV confirms active exploitation (added 2024-08-21) affecting Microsoft / Exchange Server. Unauthenticated remote administrative access may be possible. EPSS rose +43.04% over the last day, indicating growing attacker interest. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2021-31196

Name: Microsoft Exchange Server Information Disclosure Vulnerability · CISA KEV detail

Exploit added: 2024-08-21

Action due: 2024-09-11

Required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Exploit prediction scoring system (EPSS) score for CVE-2021-31196

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 3.34% 46.38% +43.04%
2 2026-03-04 4.47% 3.34% -1.13%
3 2026-03-01 — 4.47% —

Full EPSS history (60 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-31196

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.2 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.2 5.9 [email protected]
7.2 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.2 5.9 [email protected]
6.5 2.0 MEDIUM
AV:N/AC:L/Au:S/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 6.4 [email protected]

Weakness enumeration for CVE-2021-31196

Affected software / configurations for CVE-2021-31196

Vendor Product Version Raw CPE
microsoft exchange_server 2013 cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
microsoft exchange_server 2016 cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:*
microsoft exchange_server 2016 cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_21:*:*:*:*:*:*
microsoft exchange_server 2019 cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_10:*:*:*:*:*:*
microsoft exchange_server 2019 cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*

References for CVE-2021-31196

cvelogic Threat Intelligence