CVE-2026-5589: Out-of-bounds write caused by an integer underflow in the Bluetooth Mesh subsystem.

An integer underflow in btmeshsolrecv() in the Bluetooth Mesh solicitation handling (subsys/bluetooth/mesh/solicitation.c) leads to an out-of-bounds write. When CONFIGBTMESHODPRIVPROXYSRV is enabled, the function parses solicitation PDUs from raw BLE advertising payloads. The AD parsing loop reads an attacker-controlled length byte (reportedlen) and computes reportedlen - 3 without checking that reportedlen >= 3. When reportedlen is less than 3, the subtraction is performed in signed int arithmetic and yields a negative value that bypasses the length guard and is then implicitly converted to a very large sizet when passed to netbufsimplepullmem(). In builds without assertions, this wraps the buffer length and advances the data pointer far out of bounds, so subsequent reads dereference invalid memory. A nearby BLE device can trigger this with a non-connectable advertisement carrying a UUID16 AD structure and a crafted length byte, with no pairing or prior association required, potentially leading to denial of service or arbitrary code execution.