CVE-2020-35504

Guest-triggered process crash via stale SCSI request

Published May 28, 2021 · Updated Aug 4, 2024

NULL pointer dereference in QEMU SCSI emulation before 6.0.0 allows privileged guest OS users to crash the host process. In hw/scsi/esp.c, cancellation clears current_req while buffered data remains, and the next Transfer Information command dereferences that null request. A guest must have privileged access to issue the crafted SCSI command; exploitation interrupts that virtual machine's QEMU process.

CVSS severity6.0
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in QEMU SCSI emulation before 6.0.0 allows privileged guest OS users to crash the host process. In hw/scsi/esp.c, cancellation clears current_req while buffered data remains, and the next Transfer Information command dereferences that null request. A guest must have privileged access to issue the crafted SCSI command; exploitation interrupts that virtual machine's QEMU process.

The record

CVE
CVE-2020-35504
Published
May 28, 2021
Updated
Aug 4, 2024
Vendor
QEMU Project
Product
QEMU
Classifications
CWE-476, T1499
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. May 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=qemu 6.0.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

QEMU Project · QEMUversion=qemu 6.0.0

Published CVSS scores

6.0NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H
6.0CanonicalCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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