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VulnerabilityPublished Updated

CVE-2026-64034: Linux kernel · net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.3 Critical · fixed in a201c66edf2ebc6cfdc3813a889ba20fecebfae3 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score
9.3Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in a201c66edf2ebc6cfdc3813a889ba20fecebfae3, 6180a06bbc99fd9114b8db4be6c4d46e40f046ef, 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7 +4
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < a201c66edf2ebc6cfdc3813a889ba20fecebfae3
Fixed in
  • a201c66edf2ebc6cfdc3813a889ba20fecebfae3
LinuxLinuxAffected
  • ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 6180a06bbc99fd9114b8db4be6c4d46e40f046ef
Fixed in
  • 6180a06bbc99fd9114b8db4be6c4d46e40f046ef
LinuxLinuxAffected
  • ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7
Fixed in
  • 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7
LinuxLinuxAffected
  • ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 70ad2dff8d052a85dfef15715b531f38a29108cf
Fixed in
  • 70ad2dff8d052a85dfef15715b531f38a29108cf
LinuxLinuxAffected
  • ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870
Fixed in
  • 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870
LinuxLinuxAffected
  • ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 09ec063d87c2dd3fa6f3561361a017bd882e9f37
Fixed in
  • 09ec063d87c2dd3fa6f3561361a017bd882e9f37

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().

References

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