CVE-2026-13480 Out-of-bounds read in LoRaWAN fragmented data block transport (FUOTA) downlink handler
An attacker with session keys can trigger an out-of-bounds read in the LoRaWAN FUOTA handler, potentially exposing adjacent static memory contents.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-13480?
CVE-2026-13480 is a low-severity vulnerability in Zephyrproject Zephyr, published on 26 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The LoRaWAN TS004 Fragmented Data Block Transport handler frag_transport_package_callback() in subsys/lorawan/services/frag_transport.c parses downlink command bytes without validating that enough payload bytes remain before each access. The loop's only bound is rx_pos < len; after consuming the one-byte command id the handler cast rx_buf + rx_pos to a 10-byte struct frag_transport_setup_req, and for a DATA_FRAGMENT command passed &rx_buf[rx_pos] to the fragment decoder, which reads exactly ctx.frag_size bytes — with no remaining-length check in either case.
The fragment size is attacker-chosen in a preceding FRAG_SESSION_SETUP command (ctx.frag_size = req->frag_size, capped at CONFIG_LORAWAN_FRAG_TRANSPORT_MAX_FRAG_SIZE, default 232). rx_buf aliases the 255-byte static MacCtx.RxPayload buffer in the loramac-node MAC layer, while len is the actual decrypted payload length. By padding a downlink with mismatched-index DATA_FRAGMENT filler commands (each advancing rx_pos by three bytes without producing an answer) and appending one matching-index fragment near the end of the payload, an attacker can make the decoder read up to roughly frag_size bytes past the end of RxPayload, copying adjacent static memory into the decoder buffers and the FUOTA flash image.
The handler runs only on downlinks that have already passed the LoRaWAN frame MIC and FRMPayload decryption, so the defect is reachable only by a party holding the device's session keys (the FUOTA server or an attacker who has compromised those keys). The out-of-bounds bytes are never returned to the sender — the only uplink emitted is a status answer carrying fragment counts — so there is no direct disclosure channel, and on typical flat-memory LoRaWAN MCUs the over-read stays within mapped memory, making a crash unlikely. The impact is therefore a bounded out-of-bounds read with limited confidentiality consequence and no write or control-flow primitive. The fix adds remaining-length guards before each access.
Which versions are affected by CVE-2026-13480?
It affects 1 product.
Products include Zephyrproject Zephyr.
How do I fix CVE-2026-13480?
No fix has been published for CVE-2026-13480 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-13480 being exploited?
There is no known exploitation of CVE-2026-13480 in the wild and no public exploit code.
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Sources
Also known as GHSA-845m-2m84-g5h2.