How severe is CVE-2021-33881?

CVE-2021-33881 has a CVSS 3.x base score of 4.2, rated medium severity. It is exploitable over physical access with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-33881 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33881?

CVE-2021-33881 primarily affects Nxp Mifare Ultralight Ev1 Firmware. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-33881?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-33881 published?

CVE-2021-33881 was published on 2021-06-06 and last updated on 2026-06-17.

CVE-2021-33881

CVE-2021-33881 is a medium-severity vulnerability in Nxp Mifare Ultralight Ev1 Firmware with a CVSS 3.x base score of 4.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-863.

Key facts

Severity: Medium (CVSS 3.x base score 4.2)
CVSS v2: 1.9
EPSS exploit prediction: 0% (33rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Nxp Mifare Ultralight Ev1 Firmware
Published: 2021-06-06
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-33881?: 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.
How severe is CVE-2021-33881?: CVE-2021-33881 has a CVSS 3.x base score of 4.2, rated medium severity. It is exploitable over physical access with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-33881 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33881?: CVE-2021-33881 primarily affects Nxp Mifare Ultralight Ev1 Firmware. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-33881?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-33881 published?: CVE-2021-33881 was published on 2021-06-06 and last updated on 2026-06-17.

References

Affected products (8)

cpe:2.3:o:nxp:mifare_ultralight_ev1_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:mifare_ultralight_c_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:mifare_ultralight_nano_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:ntag_210_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:ntag_212_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:ntag_213_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:ntag_215_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:nxp:ntag_216_firmware:-:*:*:*:*:*:*:*

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