Auth bypass in Nxp Mifare Ultralight C
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.2 (Medium). Vector: CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (32.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 32.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- blog.quarkslab.com/rfid-monotonic-counter-anti-tearing-defeated.html (Third Party Advisory, Mitigation)
- www.nxp.com/docs/en/application-note/AN13089.pdf (Vendor Advisory)
- www.nxp.com/docs/en/application-note/AN11340.pdf (Vendor Advisory)
- www.sstic.org/2021/presentation/eeprom_it_will_all_end_in_tears/ (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-33881?
- CVE-2021-33881 is a medium-severity vulnerability in Nxp Mifare Ultralight C, classified under Incorrect Authorization. CVSS score: 4.2/10. Published 2021-06-06.
- How severe is CVE-2021-33881?
- Medium severity. CVSS v3 base score is 4.2 out of 10.
- Is CVE-2021-33881 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.