CVE-2021-28482 [High] | RCE in Exchange Server

CVE-2021-28482 is rated High Risk (74.9/100): CVSS High severity, with high exploitation likelihood (EPSS 81.87%, 99th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +9.95% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-20	71.92%	81.87%	+9.95%
2	2026-04-20	81.42%	71.92%	-9.50%
3	2026-04-13	—	81.42%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-20

71.92%

81.87%

+9.95%

2026-04-20

81.42%

71.92%

-9.50%

2026-04-13

—

81.42%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.8	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/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:L) A normal user session is enough; they don’t have to be admin. 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.	2.8	5.9	[email protected]
8.8	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/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:L) A normal user session is enough; they don’t have to be admin. 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.	2.8	5.9	[email protected]
9.0	2.0	HIGH	`AV:N/AC:L/Au:S/C:C/I:C/A:C` 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:C) Complete confidentiality impact. Integrity impact (I:C) Complete integrity impact. Availability impact (A:C) Complete availability impact.	8.0	10.0	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.8

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/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:L): A normal user session is enough; they don’t have to be admin.
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.

2.8

5.9

[email protected]

8.8

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/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:L): A normal user session is enough; they don’t have to be admin.
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.

2.8

5.9

[email protected]

9.0

2.0

HIGH

AV:N/AC:L/Au:S/C:C/I:C/A:C 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:C): Complete confidentiality impact.
Integrity impact (I:C): Complete integrity impact.
Availability impact (A:C): Complete availability impact.

8.0

10.0

[email protected]

Affected software / configurations for CVE-2021-28482

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_19::::::
microsoft	exchange_server	2016	cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20::::::
microsoft	exchange_server	2019	cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8::::::
microsoft	exchange_server	2019	cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9::::::

References for CVE-2021-28482

URL	Tags
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28482	Patch Vendor Advisory

URL

CVE-2021-28482 | Microsoft Exchange Server Remote Code Execution Vulnerability

Exploit prediction scoring system (EPSS) score for CVE-2021-28482

Common vulnerability scoring system (CVSS) metrics for CVE-2021-28482

Weakness enumeration for CVE-2021-28482

Affected software / configurations for CVE-2021-28482

References for CVE-2021-28482