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AndroidOperating system · Google

CVE-2021-25490

MEDIUM · 6.0 CVSS v3.1 Published 2021-10-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
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
A keyblob downgrade attack in keymaster prior to SMR Oct-2021 Release 1 allows attacker to trigger IV reuse vulnerability with privileged process.

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 · moderate confidence

A keyblob downgrade attack in Android's keymaster (hardware-backed key storage) allows an attacker to force the system to use older, insecure keyblob formats that contain an Initialization Vector (IV) reuse vulnerability. This IV reuse in cryptographic operations can compromise confidentiality of encrypted data.

MitigationUpdate device firmware to Samsung SMR Oct-2021 Release 1 or later which contains the patched keymaster implementation. This is a vendor-supplied patch that must be obtained through official device update channels.

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:= 9.0= 10.0= 11.0

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
Local
Complexity
Low
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

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. Identify Android OS version
    Navigate to Settings > About Phone > Android version, or run 'getprop ro.build.version.release' via ADB
    Affected if The reported version is 9.0, 10.0, or 11.0 exactly
  2. Verify keymaster hardware-backed key storage is in use
    Check if the device uses hardware-backed keystore by reviewing keymaster implementation logs or system properties (getprop keymaster.*), or examine /vendor/etc/init/android.hardware.keymaster* service configurations
    Affected if Keymaster hardware-backed key storage is enabled and in use on the device
  3. Confirm keyblob format handling
    Analyze keymaster keyblob creation and import processes via logcat (filter: keymaster, keystore) or inspect TEE logs if accessible. Look for evidence that older keyblob format versions (pre-downgrade protection) can be requested or accepted.
    Affected if The system accepts or processes keyblob format downgrade requests to version 0 or older formats
  4. Check firmware patch level
    Run 'getprop ro.build.version.security_patch' via ADB to retrieve the security patch date, or check Settings > About Phone > Security patch level
    Affected if The security patch level is earlier than October 2021 (SMR Oct-2021 Release 1 or later required for Samsung devices)

A device is affected if it runs Android 9.0, 10.0, or 11.0, uses keymaster hardware-backed keystore, and has not received the October 2021 or later security/firmware update that prevents keyblob format downgrade.

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

Update device firmware to Samsung SMR Oct-2021 Release 1 or later which contains the patched keymaster implementation. This is a vendor-supplied patch that must be obtained through official device update channels.

Recommended fix High confidence

SMR Oct-2021 Release 1 (October 2021 Samsung Security Patch Level)

  1. Check current Android security patch level on the device in Settings > About Phone > Software Information > Security patch level
  2. Navigate to Settings > Software Update and tap 'Download and install' or 'Check for updates'
  3. Download and install the October 2021 Samsung security update (SMR Oct-2021 Release 1)
  4. Verify the security patch level has been updated to October 1, 2021 or later after reboot
Caveat Security updates are cumulative; installing the October 2021 patch should not introduce functional breaking changes

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

Fix this in Android Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA6.0 h
30.0 hours of engineering $5,120
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Scan for this in your stack

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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-2021-25490 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