CVE-2021-23842 [Medium] | Security Vulnerability in Amc2 Firmware

Communication to the AMC2 uses a state-of-the-art cryptographic algorithm for symmetric encryption called Blowfish. An attacker could retrieve the key from the firmware to decrypt network traffic between the AMC2 and the host system. Thus, an attacker can exploit this vulnerability to decrypt and modify network traffic, decrypt and further investigate the device\'s firmware file, and change the device configuration. The attacker needs to have access to the local network, typically even the same subnet.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.03%	0.14%	+0.12%
2	2025-03-30	0.05%	0.03%	-0.03%
3	2025-03-29	—	0.05%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.03%

0.14%

+0.12%

2025-03-30

0.05%

0.03%

-0.03%

2025-03-29

—

0.05%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.7	3.1	MEDIUM	`CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N` Click to expand Attack vector (AV:A) Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet. 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:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. 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:N) Data isn’t meaningfully altered or forged. Availability (A:N) Service keeps running; no real outage angle.	2.1	3.6	[email protected]
7.1	3.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. 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:N) Service keeps running; no real outage angle.	1.8	5.2	[email protected]
3.6	2.0	LOW	`AV:L/AC:L/Au:N/C:P/I:P/A:N` Click to expand Access vector (AV:L) Requires local access to the target system. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	3.9	4.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.7

3.1

MEDIUM

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

Attack vector (AV:A): Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
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:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
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:N): Data isn’t meaningfully altered or forged.
Availability (A:N): Service keeps running; no real outage angle.

2.1

3.6

[email protected]

7.1

3.1

HIGH

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
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:N): Service keeps running; no real outage angle.

1.8

5.2

[email protected]

3.6

2.0

LOW

AV:L/AC:L/Au:N/C:P/I:P/A:N Click to expand

Access vector (AV:L): Requires local access to the target system.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:N): No availability impact.

3.9

4.9

[email protected]

Affected software / configurations for CVE-2021-23842

Vendor	Product	Version	Raw CPE
bosch	amc2_firmware	—	cpe:2.3:o:bosch:amc2_firmware:-:::::::*
bosch	access_management_system	3.0	cpe:2.3:a:bosch:access_management_system:3.0:::::::*
bosch	access_professional_edition	<= 3.8.0	cpe:2.3:a:bosch:access_professional_edition::::::::
bosch	building_integration_system	< 4.9.1	cpe:2.3:a:bosch:building_integration_system::::::::

References for CVE-2021-23842

URL	Tags
https://psirt.bosch.com/security-advisories/BOSCH-SA-940448-BT.html	Mitigation Vendor Advisory

URL

CVE-2021-23842 | Use of Hard-coded Cryptographic Key

Exploit prediction scoring system (EPSS) score for CVE-2021-23842

Common vulnerability scoring system (CVSS) metrics for CVE-2021-23842

Weakness enumeration for CVE-2021-23842

Affected software / configurations for CVE-2021-23842

References for CVE-2021-23842