CVE-2021-33881

Exp

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.

Published: 2021-06-06 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33881 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.41%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-33881

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-33881

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.07% 0.41% +0.34%
2 2023-03-07 1.02% 0.07% -0.94%
3 2022-04-01 — 1.02% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33881

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.2 3.1 MEDIUM
CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N 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:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 0.5 3.6 [email protected]
1.9 2.0 LOW
AV:L/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 3.4 2.9 [email protected]

Weakness enumeration for CVE-2021-33881

Affected software / configurations for CVE-2021-33881

Vendor Product Version Raw CPE
nxp mifare_ultralight_ev1_firmware — cpe:2.3:o:nxp:mifare_ultralight_ev1_firmware:-:*:*:*:*:*:*:*
nxp mifare_ultralight_c_firmware — cpe:2.3:o:nxp:mifare_ultralight_c_firmware:-:*:*:*:*:*:*:*
nxp mifare_ultralight_nano_firmware — cpe:2.3:o:nxp:mifare_ultralight_nano_firmware:-:*:*:*:*:*:*:*
nxp ntag_210_firmware — cpe:2.3:o:nxp:ntag_210_firmware:-:*:*:*:*:*:*:*
nxp ntag_212_firmware — cpe:2.3:o:nxp:ntag_212_firmware:-:*:*:*:*:*:*:*
nxp ntag_213_firmware — cpe:2.3:o:nxp:ntag_213_firmware:-:*:*:*:*:*:*:*
nxp ntag_215_firmware — cpe:2.3:o:nxp:ntag_215_firmware:-:*:*:*:*:*:*:*
nxp ntag_216_firmware — cpe:2.3:o:nxp:ntag_216_firmware:-:*:*:*:*:*:*:*

References for CVE-2021-33881

cvelogic Threat Intelligence