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

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-25 · updated 2026-10-19
Weakness: CWE-787

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.

Affected products

Linux kernel: from 2.6.26 before 5.10.261; from 5.11 before 5.15.212; from 5.16 before 6.1.178; from 6.2 before 6.6.145; from 6.7 before 6.12.96; from 6.13 before 6.18.39 — fixed in 5.10.261, 5.15.212, 6.1.178, 6.12.96, 6.18.39, 6.6.145

How to fix

Upgrade to a fixed version: Linux kernel 5.10.261, 5.15.212, 6.1.178, 6.12.96. Check the vendor advisory for mitigations.

References

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