FUOTA session denial via zero fragment index
Published Aug 14, 2026 · Updated Aug 14, 2026
Out-of-bounds write in Zephyr RTOS 3.7.0 through 4.4.2 allows remote authenticated users to disrupt FUOTA via LoRaWAN downlinks. frag_transport_package_callback() forwards a zero 1-indexed fragment counter to FragDecoderProcess(), whose fragCounter - 1 write corrupts adjacent decoder state. An active fragmentation session and valid LoRaWAN downlink authentication are required; the result is denial of that firmware-update session, not code execution.
Summary
What happened
Out-of-bounds write in Zephyr RTOS 3.7.0 through 4.4.2 allows remote authenticated users to disrupt FUOTA via LoRaWAN downlinks. frag_transport_package_callback() forwards a zero 1-indexed fragment counter to FragDecoderProcess(), whose fragCounter - 1 write corrupts adjacent decoder state. An active fragmentation session and valid LoRaWAN downlink authentication are required; the result is denial of that firmware-update session, not code execution.
The record
- CVE
- CVE-2026-12363
- Published
- Aug 14, 2026
- Updated
- Aug 14, 2026
- Vendor
- Zephyr Project
- Product
- Zephyr RTOS
- Classifications
- CWE-787, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 14, 2026CVE publishedPublication date reported by the CVE source.
- Aug 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3.7.0 <4.5.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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