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AndroidOperating system · Google

CVE-2021-25518

MEDIUM · 6.7 CVSS v3.1 Published 2021-12-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
69/100
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
An improper boundary check in secure_log of LDFW and BL31 prior to SMR Dec-2021 Release 1 allows arbitrary memory write and code execution.

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 boundary check vulnerability in the secure_log function of LDFW and BL31 (ARM Trusted Firmware) allows an attacker to write to arbitrary memory locations and achieve code execution. This affects the secure monitor layer, giving potential attackers significant control over the trusted execution environment.

MitigationUpdate LDFW and BL31 firmware to SMR Dec-2021 Release 1 or later to obtain the patched secure_log function with proper boundary checks.

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
High

CVSS:3.1/AV:L/AC:L/PR:H/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 Android version
    Run 'getprop ro.build.version.release' or check Settings > About Phone > Android version
    Affected if The device runs Android 9.0, 10.0, or 11.0 exactly (note: only these specific versions are affected)
  2. Identify BL31 firmware version
    Access the firmware version through vendor-specific tools (such as 'cat /sys/firmware/fdt' or vendor diagnostic interfaces), or consult device manufacturer documentation for how to retrieve BL31 version information
    Affected if The BL31 firmware version is earlier than the SMR Dec-2021 Release 1 patch level (the fixed version)
  3. Identify LDFW firmware version
    Check device firmware or bootloader information through vendor-specific diagnostic interfaces or documentation - LDFW (Loader Data Firmware) version is typically retrieved via low-level firmware inspection tools
    Affected if The LDFW version predates the SMR Dec-2021 Release 1 patch that includes the fixed secure_log function
  4. Verify secure_log function accessibility
    The secure_log function is part of the ARM Trusted Firmware secure monitor layer - determine if the secure monitor is accessible or if debugging interfaces expose this function (typically requires privileged access or specific firmware debugging tools)
    Affected if The secure_log function is present and accessible in the current firmware without proper boundary check validation

A device is affected if it runs Android 9.0, 10.0, or 11.0 and has BL31 or LDFW firmware versions earlier than the SMR Dec-2021 Release 1 patch level.

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 LDFW and BL31 firmware to SMR Dec-2021 Release 1 or later to obtain the patched secure_log function with proper boundary checks.

Recommended fix High confidence

SMR Dec-2021 Release 1 (or later SMR containing the fix)

  1. Identify the specific Samsung device model number (e.g., SM-G9xx, SM-N9xx, etc.)
  2. Navigate to Samsung's official firmware database or use Samsung's firmware update tool
  3. Check for and download the SMR Dec-2021 Release 1 (SMR-Jan-2022 Release 1 or later) for the specific device model
  4. Install the firmware update via Samsung's standard update mechanism (OTA or Odin/Heimdall flashing tool)
  5. Verify the installed firmware version matches the patched release
Caveat Firmware updates may reset device to factory default; backup data before flashing; flashing bootloader/firmware may void warranty and can brick device if done incorrectly

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

Fix this in Android Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing16.0 h
  • Review / QA8.0 h
48.0 hours of engineering $8,320
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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-2021-25518 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