CVE-2021-33478 [Medium] | Memory Corruption in Ip Phone 8800 Firmware

The TrustZone implementation in certain Broadcom MediaxChange firmware could allow an unauthenticated, physically proximate attacker to achieve arbitrary code execution in the TrustZone Trusted Execution Environment (TEE) of an affected device. This, for example, affects certain Cisco IP Phone and Wireless IP Phone products before 2021-07-07. Exploitation is possible only when the attacker can disassemble the device in order to control the voltage/current for chip pins.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.08%	0.30%	+0.23%
2	2025-03-30	0.15%	0.08%	-0.07%
3	2025-03-29	—	0.15%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.08%

0.30%

+0.23%

2025-03-30

0.15%

0.08%

-0.07%

2025-03-29

—

0.15%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
6.8	3.1	MEDIUM	`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:P) Hands-on access—USB, keyboard, opening the case—not something you do purely over the wire. 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: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.	0.9	5.9	[email protected]
4.6	2.0	MEDIUM	`AV:L/AC:L/Au:N/C:P/I:P/A:P` 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:P) Partial availability impact.	3.9	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

6.8

3.1

MEDIUM

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

Attack vector (AV:P): Hands-on access—USB, keyboard, opening the case—not something you do purely over the wire.
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: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.

0.9

5.9

[email protected]

4.6

2.0

MEDIUM

AV:L/AC:L/Au:N/C:P/I:P/A:P 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:P): Partial availability impact.

3.9

6.4

[email protected]

Affected software / configurations for CVE-2021-33478

Vendor	Product	Version	Raw CPE
cisco	ip_phone_8800_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8800_firmware::::::::
cisco	ip_phone_8800_series_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8800_series_with_multiplatform_firmware::::::::
cisco	ip_phone_8811_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8811_firmware::::::::
cisco	ip_phone_8811_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8811_with_multiplatform_firmware::::::::
cisco	ip_phone_8841_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8841_firmware::::::::
cisco	ip_phone_8841_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8841_with_multiplatform_firmware::::::::
cisco	ip_phone_8845_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8845_firmware::::::::
cisco	ip_phone_8845_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8845_with_multiplatform_firmware::::::::
cisco	ip_phone_8851_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8851_firmware::::::::
cisco	ip_phone_8851_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8851_with_multiplatform_firmware::::::::
cisco	ip_phone_8861_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8861_firmware::::::::
cisco	ip_phone_8861_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8861_with_multiplatform_firmware::::::::
cisco	ip_phone_8865_firmware	< 14.0\(1\)	cpe:2.3:o:cisco:ip_phone_8865_firmware::::::::
cisco	ip_phone_8865_with_multiplatform_firmware	< 11.3\(4\)	cpe:2.3:o:cisco:ip_phone_8865_with_multiplatform_firmware::::::::
cisco	wireless_ip_phone_8821_firmware	< 11.0\(6\)sr1	cpe:2.3:o:cisco:wireless_ip_phone_8821_firmware::::::::

References for CVE-2021-33478

URL	Tags
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-brcm-mxc-jul2021-26LqUZUh	Vendor Advisory

URL

CVE-2021-33478

Exploit prediction scoring system (EPSS) score for CVE-2021-33478

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33478

Weakness enumeration for CVE-2021-33478

Affected software / configurations for CVE-2021-33478

References for CVE-2021-33478