VulnerabilityPublished 25 Jul 2026

CVE-2026-64527: Linux kernel · drm/hyperv: validate VMBus packet size in receive callback

Affects Linux kernelSource GCVE Database

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Not known to be exploited.

Data as of 3 Nov 2026, 18:43 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 3 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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.

What to do

AI-suggested

A fix has been implemented in the Linux kernel to validate VMBus packet sizes before processing and to reject malformed packets with logging. Users should update to a Linux kernel version that includes this patch once available. Until then, no specific workaround is indicated. Monitor vendor advisories for official patch releases.

Description

A vulnerability in the Linux kernel's drm/hyperv component allowed improper validation of VMBus packet sizes in the receive callback. This could lead to reading residual data from prior messages due to unchecked memcpy operations. The issue was addressed by validating packet sizes before processing and rejecting malformed packets with logging.

Impact

The vulnerability could allow a consumer in the Linux kernel's Hyper-V DRM driver to read residual data from prior messages, potentially exposing unintended memory contents. There is no indication of remote code execution or privilege escalation. The issue primarily concerns data integrity and information leakage within the kernel's Hyper-V communication channel.

Summary

The Linux kernel's drm/hyperv subsystem had a flaw in hyperv_receive_sub() where it read message types and copied data without verifying the actual bytes received from the host. This could cause memcpy to copy up to 16 KiB of leftover data from previous messages, potentially exposing stale data. The fix involved passing the actual bytes received to hyperv_receive_sub(), validating packet sizes against expected headers and payloads, and rejecting packets that do not meet size requirements. Variable-length responses are carefully validated by checking resolution counts. The copy operation is now gated on successful packet reception to avoid buffer overflows. Malformed packets are logged rather than silently dropped, improving robustness.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 3 Nov 2026, 18:43 UTC

Technical details

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