ntfs3: bound to_move in indx_insert_into_root before hdr_insert_head

Summary

In the Linux kernel, the following vulnerability has been resolved: ntfs3: bound to_move in indx_insert_into_root before hdr_insert_head indx_insert_into_root() promotes a full resident $INDEX_ROOT into $INDEX_ALLOCATION and copies all non-last resident root entries into a newly allocated INDEX_BUFFER via hdr_insert_head(). The source byte count 'to_move' is summed from the on-disk resident entry sizes and is independent of the destination buffer size, which comes from root->index_block_size (via indx->index_bits). A crafted NTFS image that keeps a valid, full resident root but shrinks root->index_block_size down to 512 after the root has been populated makes hdr_insert_head() memcpy attacker-controlled resident entry bytes past the end of the kmalloc(1u << indx->index_bits) allocation returned by indx_new(). For a 512-byte destination and a resident root whose non-last entries total 560 bytes, the memcpy overruns by 120 bytes and a following memmove extends the highest written offset to 136 bytes past the allocation. The overflow bytes are a direct copy of on-disk entries (via kmemdup), so they are fully attacker-controlled. The write is reachable from unprivileged open(O_CREAT) on a mounted crafted NTFS image: a single sufficiently long create in a directory whose resident root is already full forces root promotion and triggers the copy. This is a controlled out-of-bounds write of 120-136 bytes past a kmalloc(index_block_size) allocation, with attacker-controlled content. It is a bounded adjacent-heap corruption primitive; it is not an arbitrary-address write. Successful exploitation into a named victim object depends on the surrounding slab layout. Reject the copy at the sink. The destination's INDEX_HDR already reports hdr_total (the payload capacity of the new buffer) and hdr_used (the bytes already consumed by the terminal END entry installed by indx_new()); require that to_move fits in the remaining payload before calling hdr_insert_head(). On mismatch, fail with -EINVAL and mark the filesystem as having a detected on-disk inconsistency, which is the same behaviour as the surrounding validation in this function.

Timeline

1. Aug 15, 2026, 5:53 AM UTCCVE published
2. Oct 16, 2026, 6:43 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: total

3. Oct 16, 2026, 6:45 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in 0af83b8155cc848e9f5d2c36e20a70d024214649; From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in cb3161deebcaf8d36d3115abf452c633f2180fc1; From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in 53c5f3b2da3774b41534728aba295c098c9efa19; From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in 194b00c99ba971fa7cf6acd747a36032c6de54eb; From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in aaa1f956c0fc41089a4a534da7df91552a08a47c; From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in d240f5f9d036b8180224954d9873f172b6be4dd8; From 82cae269cfa953032fbb8980a7d554d60fb00b17 · fixed in 9b6926ac9c970ae0b2c2fe6289b16e9aa10b6a67

• Linux Linux

  5.15

• KernelLinux

  From 5.15.0 · fixed in 5.15.212; From 5.16.0 · fixed in 6.1.178; From 6.2.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5

References 7