Wii system flaws

This page documents the various bugs in the Wii.

Hardware

Summary	Description	Successful exploitation result	Fixed in hardware revision	Discovered	Discovered by
HW_BOOT0 not clear-only	To prevent boot0 from being dumped, boot2 clears register HW_BOOT0 that allows the boot0 ROM to be read. However, Nintendo forgot to make this register clear-only, so simply re-enabling it allows boot0 to be dumped from 0xFFFE0000 or 0xFFFF0000 in memory.	boot0 can be obtained.	Unfixed	May 2008	fail0verflow
DVD-Video support is inadequately protected	While the Wii was initially meant to support DVD playback, it was scrapped to avoid needing to pay licensing fees. This support was removed in later revisions of the disc drive. However, when the Hollywood register ahbprot is disabled (e.g. by The Homebrew Channel), or diflags is enabled, homebrew can be used to read DVDs.	DVDs can be read on the Wii.	Unknown	July 2008	fail0verflow

boot1

Summary	Description	Successful exploitation result	Fixed in boot1 version	Discovered	Discovered by
strncmp used to compare hashes	boot1 verifies the signature of boot2 before booting it, however, the signing bug is present, allowing a fake boot2 to be loaded.	A custom bootloader can be installed, such as BootMii.	boot1c	January 2008	fail0verflow
HW_BOOT0 is not cleared until boot2	When the Wii boots, boot2 clears HW_BOOT0 to unmap boot0 and prevent it from being dumped. However, when boot2 is replaced through the signing bug, HW_BOOT0 is not yet cleared.	Dumping of boot0	Unfixed	January 2008	fail0verflow

boot2

Summary	Description	Successful exploitation result	Fixed in boot2 version	Discovered	Discovered by
No signature checks	Unlike boot1, boot2 does not check the signature of titles it launches, which means they can be freely modified.	Modifying the System Menu or System Menu IOS does not brick the system, and a custom MIOS can be loaded this way.	Unfixed	Unknown	fail0verflow

IOS

Module	Summary	Description	Successful exploitation result	Fixed in system update	Discovered	Discovered by
Kernel	No sanity checks on arguments passed to get_kernel_flavor and get_unk_flavor	System calls get_kernel_flavor and get_unk_flavor do not check to ensure that the pointers passed are appropriate to write to; they will write to any addresses.	If IOS code execution is gained, any address can be overwritten to some specific values by passing those addresses into get_kernel_flavor or get_unk_flavor.	Unknown	Unknown	fail0verflow
Kernel	Default keys exist in the kernel binary.	The Wii includes an OTP bank of memory, which contains securely stored keys. However, IOS includes a copy of these keys, which it falls back to if the OTP keys are missing. Because these keys are identical, the OTP keys can easily be extracted from the IOS kernel binary if it is dumped.	Most OTP keys can be obtained.	Unfixed[check]	December 2007	fail0verflow
ES	Trucha bug	The Wii used the strncmp function to check signatures, which always stopped at the first null byte, weakening the security. More information can be found at signing bug.	Custom titles can be installed, and fakesigned discs can be played.	3.3 (IOS30 only), October 23 Update (still exploitable by IOS16 pirates), 4.0	Unknown	fail0verflow and xt5 (independently)
ES	Title signatures are only checked at installation time.	NAND title signatures are checked on install, but never on launch. This means that if a title can be installed, it can be launched without further exploitation. This applies to both IOSes and apps, including the System Menu.	One-time exploitation leads to trivial persistence.	Unfixed	June 2008	fail0verflow
ES	No address check in ES_GetTitles	One of the parameters of ES_GetTitles is a buffer address for the titles to be written, however, this address is not checked to ensure that it is a Broadway-accessible address. By passing an address to overwrite, the titles fetched will be placed there.	Any address accessible from the ES module can be overwritten.	Unfixed	February 2020	Fullmetal5
ES	ES_DiVerify does not check the calling module	ES contains no checks when ES_DiVerify is called, responding to any module that calls it. By sending this call from the Broadway over IPC, ES will receive this from the PPCBOOT process, and proceed normally.	Homebrew can identify as any title.	4.0	March 2008	fail0verflow and Waninkoko (independently)
ES	ES_AddTitleFinish does not check signatures	ES_AddTitleFinish does not check the signature of the title passed to ES_AddTitleStart, as it expects the signature to be valid by that point. By changing the contents of /import before calling ES_AddTitleFinish, any title can be installed.	Installation of any title	4.3	Unknown	Unknown
ES	No out-of-bounds check when determining the common key from the ticket	Korean titles have a byte that is set to 0 to use the normal common key, and 1 to use the Korean key. This value is used as an index in an array containing the locations of both common keys. However, the value is never sanity checked, so any value can be inserted.	Arbitrary common key usage	Unknown	September 2008	fail0verflow
FS	/dev/flash is unprotected	Permission checks in IOS exist for files, but the FS module does not check for permissions when reading the raw NAND contents. If the NAND key is obtained, the NAND can be freely modified.	Arbitrary NAND modification	3.4[check]	Unknown	Unknown
STM	STM release bug	The state transition manager checks if a handle is invalid before releasing it, but forgets to actually refuse to release it if it is invalid. More information can be seen at STM Release Exploit	Control over IOS can be gained.	4.0	Unknown	fail0verflow, Anonymous person (from reverse engineering Homebrew Channel installer)

System Menu

Summary	Description	Successful exploitation result	Fixed in system update	Discovered	Discovered by
Buffer overflow in mail parser	When parsing a message saved to the SD Card, the Wii Message Board has a buffer overflow bug when copying the message body. By overwriting the memory allocation table this way, the next allocation address can be placed on the stack, allowing code to be returned to. LetterBomb and Wilbrand exploit this.	Code execution in the System Menu	Unfixed	August 2011	fail0verflow and giantpune (independently)
Twilight Hack check only checks one zeldaTp.dat	The savefile check to prevent Twilight Hack returns after checking one zeldaTp.dat. By placing a legitimate zeldaTp.dat somewhere else in the file, the real zeldaTp.dat can bypass the check.	A new version of the Twilight Hack works.	3.4	June 2008	fail0verflow
Twilight Hack check allows all unaligned zeldaTp.dat sizes	The savefile check that prevents Twilight Hack checks the number of bytes read against the file size, aligned to 32 bytes. By leaving the size misaligned, the checker will go past it without deleting it.	The new Twilight Hack survives Broadway resets.	3.4	June 2008	fail0verflow
Twilight Hack check only looks at the last zeldaTp.dat file	When fixing the 3.3 bugs in the Twilight Hack checker, Nintendo started only checking the final zeldaTp.dat found. By placing a legitimate save later in the WAD, the checker can be bypassed once again.	Another Twilight Hack works on 3.4.	4.0	November 2008	fail0verflow

BC

Summary	Description	Successful exploitation result	Fixed in BC version	Discovered	Discovered by
strncmp used to compare hashes	BC verifies the signature of boot2 before booting it, however, the signing bug is present, allowing a fake boot2 to be loaded.	If a fakesigned boot2 is installed, GameCube mode will launch it fine.	v4	January 2008	fail0verflow

MIOS

Summary	Description	Successful exploitation result	Fixed in MIOS version	Discovered	Discovered by
Memory not cleared before booting GC game	When MIOS loads a GameCube game, it never clears the 48K bytes of memory that the game should not have access to. By using a pair of tweezers to change the address lines, the entire memory can be dumped.	MIOS and the rest of memory can be dumped using GameCube homebrew.	v8	Unknown	fail0verflow
No boot2 signature check	When the power button is pressed in GameCube mode, MIOS loads boot2 in a shutdown state. However, it has no signature verification, so it is easy to reboot into software such as BootMii this way.	The Wii will not hang on shutdown from MIOS if a custom boot2 is installed.	Unfixed	Unknown	fail0verflow

Nintendo SDK

These flaws exist in every official application, because they are bundled in, probably in the official SDK. For this reason, they are very difficult to fix.

Summary	Description	Successful exploitation result	Discovered	Discovered by
No upper bound to CCB array	The Fluoride Bluetooth stack includes a function to get a CCB from an ID. This function checks whether the ID is below the lower bound, however, no upper bound is enforced. By carefully crafting an ID, a fake CCB entry can be placed in the handles array. Sending a packet to free this struct causes it to "unlink" from its adjacent entries, which can be used to get an arbitrary write, and therefore code execution.	PPC code execution (used in Bluebomb)	September 2019	Fullmetal5
No size limit to BigInts in Opera	In Opera, the dtoa module includes a number of functions operating on big integers with a maximum size, however, any sizes passed in are never checked. By passing in a value too large, the BigInt allocation table will return a smaller BigInt, which leads to a buffer overflow.	PPC code execution (used in str2hax)	December 2018	Fullmetal5
Use-after-free in Flash objects	Flash includes a feature to watch certain properties and get notified when they change, with the ability to easily change it again by returning a value from the event handler. If the event handler decides to delete the object holding that property, the caller still sets the value at that address. With some manipulation of the garbage collector and thread-switching systems, the stack pointer can be changed, allowing ROP to begin.	ROP in the PPC (used in FlashHax)	March 2018	Fullmetal5