HOMEVULNERABILITIESCVE-2021-3527
MEDIUM

CVE-2021-3527

CWE-770Published: May 26, 2021· Updated: Jun 17, 2026

5.5
CVSS v3.1

Official Description

A flaw was found in the USB redirector device (usb-redir) of QEMU. Small USB packets are combined into a single, large transfer request, to reduce the overhead and improve performance. The combined size of the bulk transfer is used to dynamically allocate a variable length array (VLA) on the stack without proper validation. Since the total size is not bounded, a malicious guest could use this flaw to influence the array length and cause the QEMU process to perform an excessive allocation on the stack, resulting in a denial of service.

NVD Source

Technical Analysis

CVE-2021-3527 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 5.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

Debian1 product(s)
debian linux
qemu1 product(s)
qemu
Red Hat1 product(s)
enterprise linux
Source: NVD CPE · 4 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=1955695
PATCHhttps://gitlab.com/qemu-project/qemu/-/commit/05a40b172e4d691371534828078be47e7fff524c
PATCHhttps://gitlab.com/qemu-project/qemu/-/commit/7ec54f9eb62b5d177e30eb8b1cad795a5f8d8986
PATCHhttps://www.openwall.com/lists/oss-security/2021/05/05/5
PATCHhttps://bugzilla.redhat.com/show_bug.cgi?id=1955695
PATCHhttps://gitlab.com/qemu-project/qemu/-/commit/05a40b172e4d691371534828078be47e7fff524c
PATCHhttps://gitlab.com/qemu-project/qemu/-/commit/7ec54f9eb62b5d177e30eb8b1cad795a5f8d8986
PATCHhttps://www.openwall.com/lists/oss-security/2021/05/05/5
ADVISORYhttps://lists.debian.org/debian-lts-announce/2021/09/msg00000.html
ADVISORYhttps://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
ADVISORYhttps://security.gentoo.org/glsa/202208-27
ADVISORYhttps://security.netapp.com/advisory/ntap-20210708-0008/
ADVISORYhttps://lists.debian.org/debian-lts-announce/2021/09/msg00000.html
ADVISORYhttps://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
ADVISORYhttps://security.gentoo.org/glsa/202208-27
ADVISORYhttps://security.netapp.com/advisory/ntap-20210708-0008/

All References (16)

→
https://bugzilla.redhat.com/show_bug.cgi?id=1955695Issue Tracking · Patch · Third Party Advisory
→
https://gitlab.com/qemu-project/qemu/-/commit/05a40b172e4d691371534828078be47e7fff524cPatch · Third Party Advisory
→
https://gitlab.com/qemu-project/qemu/-/commit/7ec54f9eb62b5d177e30eb8b1cad795a5f8d8986Patch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/09/msg00000.htmlMailing List · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2022/09/msg00008.htmlMailing List · Third Party Advisory
→
https://security.gentoo.org/glsa/202208-27Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210708-0008/Third Party Advisory
→
https://www.openwall.com/lists/oss-security/2021/05/05/5Mailing List · Patch · Third Party Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=1955695Issue Tracking · Patch · Third Party Advisory
→
https://gitlab.com/qemu-project/qemu/-/commit/05a40b172e4d691371534828078be47e7fff524cPatch · Third Party Advisory
→
https://gitlab.com/qemu-project/qemu/-/commit/7ec54f9eb62b5d177e30eb8b1cad795a5f8d8986Patch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/09/msg00000.htmlMailing List · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2022/09/msg00008.htmlMailing List · Third Party Advisory
→
https://security.gentoo.org/glsa/202208-27Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210708-0008/Third Party Advisory

Quick Facts

CVE IDCVE-2021-3527
CVSS Score5.5 / 10
SeverityMEDIUM
WeaknessCWE-770
CISA KEVNo
Affected3 vendor(s)
PublishedMay 26, 2021

Related CVEs (CWE-770)

CVE-2018-20033
9.8
CVE-2022-3273
9.8
CVE-2025-11832
9.8
CVE-2023-38507
9.8
CVE-2022-3456
9.8
CVE-2022-3439
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-3527 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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