CVE-2026-64323: udf: validate VAT header length against the VAT inode size

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

udf: validate VAT header length against the VAT inode size

udf_load_vat() takes the virtual partition's start offset straight from
the on-disk VAT 2.0 header without checking it against the VAT inode
size:

	map->s_type_specific.s_virtual.s_start_offset =
		le16_to_cpu(vat20->lengthHeader);
	map->s_type_specific.s_virtual.s_num_entries =
		(sbi->s_vat_inode->i_size -
			map->s_type_specific.s_virtual.s_start_offset) >> 2;

lengthHeader is a fully attacker-controlled 16-bit value.  If it exceeds
the VAT inode size, the s_num_entries subtraction underflows to a huge
count, which defeats the "block > s_num_entries" bound in
udf_get_pblock_virt15(); and on the ICB-inline path that function reads

	((__le32 *)(iinfo->i_data + s_start_offset))[block]

so a large s_start_offset indexes past the inode's in-ICB data.  Mounting
a crafted UDF image with a virtual (VAT) partition then triggers an
out-of-bounds read.

Reject a VAT whose header length does not leave room for at least one
entry within the VAT inode.

The Linux kernel CVE team has assigned CVE-2026-64323 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 5.10.261 with commit 0ad2d09a8d66fa8dc6f9b70d660b5fb4478ea934
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 5.15.212 with commit 883962731420ec271ed8c1cd76524f4b17faa982
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 6.1.178 with commit 2900e02a0dd4fc30ac9840e7ce4ca0b041ab0d63
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 6.6.145 with commit bb0d384c1f42a5b7ace0bd88fee80b9bb1d49acb
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 6.12.96 with commit 55287a3555ff0515b3aff181d2c08c0462a41709
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 6.18.39 with commit e610fb113cdfa8bf4247c9bf4f2337b81ad4ddad
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 7.1.4 with commit 74580fdf022909e184223cacc364feb826982d96
	Issue introduced in 2.6.26 with commit fa5e08156335d0687c85b4e724db9448fb166601 and fixed in 7.2-rc1 with commit d8202786b3d75125c84ebc4de6d946f92fde0ee8

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64323
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/udf/super.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/0ad2d09a8d66fa8dc6f9b70d660b5fb4478ea934
	https://git.kernel.org/stable/c/883962731420ec271ed8c1cd76524f4b17faa982
	https://git.kernel.org/stable/c/2900e02a0dd4fc30ac9840e7ce4ca0b041ab0d63
	https://git.kernel.org/stable/c/bb0d384c1f42a5b7ace0bd88fee80b9bb1d49acb
	https://git.kernel.org/stable/c/55287a3555ff0515b3aff181d2c08c0462a41709
	https://git.kernel.org/stable/c/e610fb113cdfa8bf4247c9bf4f2337b81ad4ddad
	https://git.kernel.org/stable/c/74580fdf022909e184223cacc364feb826982d96
	https://git.kernel.org/stable/c/d8202786b3d75125c84ebc4de6d946f92fde0ee8