CVE-2021-3507Public exploit

Host-process crash via unchecked floppy end-of-track

Published May 6, 2021 · Updated Aug 3, 2024

Heap buffer overflow in QEMU 6.0.0 and earlier allows guest OS users to crash the host process through crafted floppy DMA reads. The floppy controller derives the DMA transfer length from a guest-supplied end-of-track value without rejecting values beyond the disk geometry, causing a heap overrun. Privileged guest access and an emulated floppy controller are required; the documented impacts are a host-process crash and potential host-memory disclosure.

CVSS severity6.1
Medium
EPSS probability0.49%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in QEMU 6.0.0 and earlier allows guest OS users to crash the host process through crafted floppy DMA reads. The floppy controller derives the DMA transfer length from a guest-supplied end-of-track value without rejecting values beyond the disk geometry, causing a heap overrun. Privileged guest access and an emulated floppy controller are required; the documented impacts are a host-process crash and potential host-memory disclosure.

The record

CVE
CVE-2021-3507
Published
May 6, 2021
Updated
Aug 3, 2024
Vendor
QEMU Project
Product
QEMU
Classifications
CWE-119, CWE-787, T1499
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. May 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=up to 6.0.0 (including)

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

QEMU Project · QEMUversion=up to 6.0.0 (including)

Published CVSS scores

6.1OracleCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
6.1NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
4.4SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L
3.6NVDAV:L/AC:L/Au:N/C:P/I:N/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-787Out-of-bounds Write
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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