CVE-2021-33881

Name: CVE-2021-33881
Creator: NVD / NIST
Published: 2021-06-06T16:15:07.407+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.2/10EPSS 0.41%

Last modified Jun 17, 2026

CVE-2021-33881 is a medium-severity vulnerability rated 4.2/10 on the CVSS scale. 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.. EPSS estimates a 0.41% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

4.2/10

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

EPSS Probability

0.41%

32.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-863

Affected Software

Vendor	Product	Versions
Nxp	Mifare Ultralight Ev1 Firmware	All versions
Nxp	Mifare Ultralight C Firmware	All versions
Nxp	Mifare Ultralight Nano Firmware	All versions
Nxp	Ntag 210 Firmware	All versions
Nxp	Ntag 212 Firmware	All versions
Nxp	Ntag 213 Firmware	All versions
Nxp	Ntag 215 Firmware	All versions
Nxp	Ntag 216 Firmware	All versions

References

https://blog.quarkslab.com/rfid-monotonic-counter-anti-tearing-defeated.htmlMitigation, Third Party Advisory
https://www.nxp.com/docs/en/application-note/AN11340.pdfVendor Advisory
https://www.nxp.com/docs/en/application-note/AN13089.pdfVendor Advisory
https://www.sstic.org/2021/presentation/eeprom_it_will_all_end_in_tears/Exploit, Third Party Advisory
https://blog.quarkslab.com/rfid-monotonic-counter-anti-tearing-defeated.htmlMitigation, Third Party Advisory
https://www.nxp.com/docs/en/application-note/AN11340.pdfVendor Advisory
https://www.nxp.com/docs/en/application-note/AN13089.pdfVendor Advisory
https://www.sstic.org/2021/presentation/eeprom_it_will_all_end_in_tears/Exploit, Third Party Advisory

Timeline

Published: Jun 6, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-33881?

How severe is CVE-2021-33881?

CVE-2021-33881 has a CVSS score of 4.2/10 (MEDIUM severity). The EPSS model estimates a 0.41% probability of exploitation in the next 30 days.

How do I fix CVE-2021-33881?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-33881?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST