dbcve.org
TizenOperating system · Linux

CVE-2021-25435

CRITICAL · 9.8 CVSS v3.1 Published 2021-07-08
Fix available
A fix is available. Upgrade to 5.5 or later.
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
Improper input validation vulnerability in Tizen bootloader prior to Firmware update JUL-2021 Release allows arbitrary code execution using recovery partition in wireless firmware download mode.

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 critical improper input validation vulnerability exists in the Tizen bootloader that allows attackers to execute arbitrary code by exploiting the recovery partition during wireless firmware download mode. The bootloader fails to properly validate input data before processing, enabling an attacker with wireless firmware download access to inject and execute malicious code with bootloader-level privileges.

MitigationApply the JUL-2021 firmware update or later to patch the bootloader input validation vulnerability. Organizations should prioritize deploying this update to all affected Tizen devices, particularly those supporting wireless firmware download functionality.

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
TizenOperating system
Affected:< 5.5

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. Identify Tizen version
    Check the installed Tizen OS version using the system information utility or by reading /etc/os-release or the tizen-version file if accessible from the device
    Affected if The reported Tizen version is lower than 5.5 (e.g., 5.0, 4.0, 3.0)
  2. Confirm bootloader component
    Verify the device runs the Tizen bootloader by checking boot-related system files or bootloader configuration files typically found in /boot or /bootloader partitions
    Affected if The device uses a Tizen-specific bootloader and supports recovery partition functionality
  3. Verify wireless firmware download support
    Check if the device configuration or firmware settings include wireless (OTA) firmware download or FOTA (Firmware Over-The-Air) update capability in the bootloader or system settings
    Affected if Wireless firmware download mode is enabled or accessible on the device
  4. Check bootloader input validation configuration
    Examine the bootloader configuration or recovery-related settings for any custom or non-standard input validation parameters, typically found in the bootloader config files or device tree
    Affected if The bootloader uses default or unpatched input validation for recovery partition processing

The device is affected if it runs Tizen Linux version below 5.5 and has wireless firmware download functionality enabled in the bootloader.

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
Upgrade available Upgrade to 5.5 or later
Fixed in 5.5
Interim mitigation

Apply the JUL-2021 firmware update or later to patch the bootloader input validation vulnerability. Organizations should prioritize deploying this update to all affected Tizen devices, particularly those supporting wireless firmware download functionality.

Recommended fix High confidence

Tizen 5.5 or later (JUL-2021 Release)

  1. Update Tizen firmware to the JUL-2021 Release or later to obtain the patched bootloader
  2. If using Tizen devices, apply the latest available firmware update that includes the July 2021 security patch
  3. Verify the bootloader has been updated by checking the firmware version after the update

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

Fix this in Tizen Scoped from the published advisory
  • Consultation8.0 h
  • Implementation24.0 h
  • Testing16.0 h
  • Review / QA8.0 h
56.0 hours of engineering $9,760
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $15,616.

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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-2021-25435 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