Zephyrs Bluetooth Classic Hands-Free Profile (HFP) Hands-Free role parser (subsys/bluetooth/host/classic/hfp_hf.c) contains an out-of-bounds write. During Service Level Connection setup the HF sends AT+CIND=? and parses the AGs +CIND: response in cind_handle(), which assigns a per-entry counter index and calls cind_handle_values() for each list element. cind_handle_values() then wrote hf-ind_table[index] = i without verifying that index is within the 20-element int8_t ind_table[] array of struct bt_hfp_hf. Because the parser places no cap on the number of +CIND: list entries, a remote Attendant Gateway (a malicious, compromised, or spoofed peer the device connects to over Bluetooth) can send a response with more than 20 recognized indicator entries and drive index arbitrarily large, writing a small attacker-positioned value past the array into adjacent struct fields (feature masks, SDP/version state, the calls[] array, work/atomic bookkeeping) and potentially beyond the static connection pool slot. This yields memory corruption and at least denial of service of the Bluetooth host, triggered by a single malformed AT response with no user interaction. The sibling consumer ag_indicator_handle_values() already performed the equivalent bounds check; this commit adds the same index = ARRAY_SIZE(hf-ind_table) guard to close the gap. Affects builds with CONFIG_BT_HFP_HF enabled; introduced with the original HFP HF CIND parser (~v1.7) and present through v4.4.0.
Weakness
The product writes data past the end, or before the beginning, of the intended buffer.
Potential Mitigations
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.
Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
Consider adhering to the following rules when allocating and managing an application’s memory:
Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.
For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].