CVE-2026-31716

Summary

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

fs/ntfs3: validate rec->used in journal-replay file record check

check_file_record() validates rec->total against the record size but never validates rec->used. The do_action() journal-replay handlers read rec->used from disk and use it to compute memmove lengths:

DeleteAttribute: memmove(attr, …, used - asize - roff) CreateAttribute: memmove(…, attr, used - roff) change_attr_size: memmove(…, used - PtrOffset(rec, next))

When rec->used is smaller than the offset of a validated attribute, or larger than the record size, these subtractions can underflow allowing us to copy huge amounts of memory in to a 4kb buffer, generally considered a bad idea overall.

This requires a corrupted filesystem, which isn't a threat model the kernel really needs to worry about, but checking for such an obvious out-of-bounds value is good to keep things robust, especially on journal replay

Fix this up by bounding rec->used correctly.

This is much like commit b2bc7c44ed17 ("fs/ntfs3: Fix slab-out-of-bounds read in DeleteIndexEntryRoot") which checked different values in this same switch statement.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/8e64d33198b5a0fb14a452708bad844f94f03b2c
• https://git.kernel.org/stable/c/1393a467a9607e62123806de7d4c3a3e54e396a9
• https://git.kernel.org/stable/c/f90b8a1798b750755a9e9aee66678f0a1820bbaf
• https://git.kernel.org/stable/c/4b1613d7e2deda831a97e427d1ea586e50fe1be5
• https://git.kernel.org/stable/c/0112e6279420d4005b3d57af36fb45c01b8d0116
• https://git.kernel.org/stable/c/f79d0403ea20a81bc29105bba54fbcab54e8c403
• https://git.kernel.org/stable/c/0ca0485e4b2e837ebb6cbd4f2451aba665a03e4b

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