VulnerabilityPublished 19 Jul 2026

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

Source GCVE Database

Authoritative record:CVE-2026-64034· Critical 9.3

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.
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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-r5hj-4chx-57cx

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < a201c66edf2ebc6cfdc3813a889ba20fecebfae3	Fixed in a201c66edf2ebc6cfdc3813a889ba20fecebfae3
LinuxLinux	Affected ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 6180a06bbc99fd9114b8db4be6c4d46e40f046ef	Fixed in 6180a06bbc99fd9114b8db4be6c4d46e40f046ef
LinuxLinux	Affected ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7	Fixed in 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7
LinuxLinux	Affected ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 70ad2dff8d052a85dfef15715b531f38a29108cf	Fixed in 70ad2dff8d052a85dfef15715b531f38a29108cf
LinuxLinux	Affected ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870	Fixed in 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870
LinuxLinux	Affected ≥ ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f, < 09ec063d87c2dd3fa6f3561361a017bd882e9f37	Fixed in 09ec063d87c2dd3fa6f3561361a017bd882e9f37

AI-suggested

A fix has been implemented in the Linux kernel to address this vulnerability by changing the code to read hwc_msg_id once atomically. Users should update to a Linux kernel version that includes this fix. No additional mitigations are indicated.

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().

Impact

This vulnerability could allow an attacker with hardware-level access to modify the hwc_msg_id value between validation and use, potentially bypassing bounds checks. This could lead to undefined behavior or security issues in the mana network driver. However, exploitation requires hardware capability to modify DMA memory during execution, limiting practical impact. No known exploits are reported.

References

Community reviews

Loading reviews…