CVE-2021-33881
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct...
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct a "tear off" attack) over RFID to bypass a Monotonic Counter protection mechanism. The impact depends on how the anti tear-off feature is used in specific applications such as public transportation, physical access control, etc.
Attack profile
How easy it is to exploit
- Attack vector
- Physical
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct a "tear off" attack) over RFID to bypass a Monotonic Counter protection mechanism. The impact depends on how the anti tear-off feature is used in specific applications such as public transportation, physical access control, etc.
- Record
CVE-2021-33881- CVSS 3.1
- 4.2 Medium
CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N - CVSS 2.0
- 1.9 Low
AV:L/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-863
- Updated
- 2026-11-02
CVE List No score
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct a "tear off" attack) over RFID to bypass a Monotonic Counter protection mechanism. The impact depends on how the anti tear-off feature is used in specific applications such as public transportation, physical access control, etc.
- Record
CVE-2021-33881- Updated
- 2026-11-02
EUVDEUVD-2021-20554 No score
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct a "tear off" attack) over RFID to bypass a Monotonic Counter protection mechanism. The impact depends on how the anti tear-off feature is used in specific applications such as public transportation, physical access control, etc.
- Record
EUVD-2021-20554- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-ff8p-pfwc-wjf2 No score
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct...
On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct a "tear off" attack) over RFID to bypass a Monotonic Counter protection mechanism. The impact depends on how the anti tear-off feature is used in specific applications such as public transportation, physical access control, etc.
- Record
GHSA-ff8p-pfwc-wjf2- Weakness
- CWE-863
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-33881 is a medium vulnerability (CVSS 4.2) in Nxp Mifare Ultralight C Firmware, published June 6, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. No source names a fixed version.