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Fencer Intel
medium 4.2

CVE-2021-33881 json

On NXP MIFARE Ultralight and NTAG cards, an attacker can interrupt a write operation (aka conduct a "tear off" attack) over RFID to bypass…

published 5y ago modified 4mo ago also EUVD-2021-20554

cvss
4.2
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

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.

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Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • sstic.org https://www.sstic.org/2021/presentation/eeprom_it_will_all_end_in_tears/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 4.2 CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:N/I:P/A:N

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.