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ZephyrOperating system · Zephyrproject

CVE-2021-3436

MEDIUM · 6.5 CVSS v3.1 Published 2021-10-05
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
74/100
Remediation priority · Elevated
Public exploit Remotely reachable No privileges Zero-click Patch available

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
BT: Possible to overwrite an existing bond during keys distribution phase when the identity address of the bond is known. Zephyr versions >= 1.14.2, >= 2.4.0, >= 2.5.0 contain Use of Multiple Resources with Duplicate Identifier (CWE-694). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j76f-35mc-4h63

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

A detailed technical summary for this CVE is being prepared.

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
ZephyrOperating system
Affected:= 1.14.2= 2.4.0= 2.5.0

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
None
Integrity
Low
Availability
Low

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

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
Patch available Apply the vendor patch
Vendor patch github.com →
Recommended fix Moderate confidence

Upgrade to the fixed Zephyr version as specified in GHSA-j76f-35mc-4h63 (typically a version newer than 2.5.0)

  1. 1. Identify the Zephyr version currently in use by checking the manifest file (typically west.yml or zephyr.yml) or the version tag in the build environment
  2. 2. Consult the Zephyr security advisory at GHSA-j76f-35mc-4h63 to identify the specific version containing the fix for CVE-2021-3436
  3. 3. Update the Zephyr manifest to reference the fixed version, changing the version field for the main zephyr repository
  4. 4. Run 'west update' to fetch the fixed version
  5. 5. Rebuild and flash the firmware with the updated Zephyr version
  6. 6. Test the Bluetooth functionality to ensure bonding works correctly and existing bonds are not overwritten
Caveat Minor: Review API changes between versions for any Bluetooth stack modifications that may affect application code

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

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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-2021-3436 in production — separate from our analysis above.

No notes yet

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What this is

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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
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