dbcve.org
AndroidOperating system · Google

CVE-2021-0956

CRITICAL · 9.8 CVSS v3.1 Published 2021-12-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In NfcTag::discoverTechnologies (activation) of NfcTag.cpp, there is a possible out of bounds write due to an incorrect bounds check. This could lead to remote escalation of privilege with no additionalSystem execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11 Android-12Android ID: A-189942532

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A bounds check error in NfcTag::discoverTechnologies within Android's NFC stack allows an out-of-bounds write when processing NFC tag activation data. By presenting a maliciously crafted NFC tag with manipulated technology parameters, an attacker can trigger the incorrect bounds check and write beyond buffer limits, achieving privilege escalation from the NFC service context to system-level privileges without user interaction.

MitigationApply the Android security patch for Android-11 and Android-12 that addresses the NfcTag bounds check vulnerability (Android ID A-189942532). Users should ensure their devices receive the latest monthly security update.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AndroidOperating system
Affected:= 11.0= 12.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check the Android version
    Go to Settings > About Phone > Android version, or run 'getprop ro.build.version.release' via ADB shell
    Affected if The version is 11.0 or 12.0 exactly (note: this vulnerability affects only these specific versions)
  2. Verify NFC hardware and service availability
    Check if NFC is present and the NFC service is running. On device: Settings > Connected devices > NFC. Via ADB: run 'nfc list' or check service status with 'dumpsys nfc'
    Affected if The device has NFC hardware and the NFC service is active or can be activated
  3. Confirm the security patch level
    Go to Settings > About Phone > Security patch level, or run 'getprop ro.build.version.security_patch' via ADB shell
    Affected if The installed security patch level predates the November 2021 Android security update

A device is affected if it runs Android 11.0 or 12.0, has NFC capability enabled, and has a security patch level earlier than November 2021.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Android security patch for Android-11 and Android-12 that addresses the NfcTag bounds check vulnerability (Android ID A-189942532). Users should ensure their devices receive the latest monthly security update.

Recommended fix High confidence

Update to the latest Android security patch level for Android 11 or Android 12 (whichever is applicable). For Android 11, the fix was included in the November 2021 security patch or later. For Android 12, the fix was included in the November 2021 security patch or later.

  1. 1. Navigate to Settings > System > Security update on the Android device
  2. 2. Check the current Security patch level in the About phone section
  3. 3. If the device is on Android 11 (version 11.0) or Android 12 (version 12.0), update to the latest available security patch level
  4. 4. Go to Settings > System > Software update (or Settings > About phone > System update)
  5. 5. Download and install any available system updates
  6. 6. Verify the Security patch level reflects the update containing the fix for CVE-2021-0956 (A-189942532)
Caveat Minimal risk; security updates typically do not introduce breaking changes. Users should ensure they back up important data before applying updates as a general precaution.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Android Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-0956 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data