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CVE-2021-3638

23
FAUCET Score

CVE-2021-3638 describes an out-of-bounds memory access vulnerability in QEMU's ATI VGA device emulation, specifically within the ati_2d_blt() routine. This flaw affects Fedora and QEMU products, occurring when a guest provides invalid destination display parameters during MMIO write operations. Rated with a CVSS score of 6.5 (Medium), this vulnerability could allow a malicious guest to trigger a denial of service on the host by crashing the QEMU process. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 4.0.0, <= 6.1.0CPE matchmatch criteria
cpe:2.3:a:qemu:qemu:*:*:*:*:*:*:*:*
36CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
37CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:37:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.0
Impact Score
4.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.43%
Probability of exploitation in next 30 days
EPSS Percentile
35.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0043 is in the 90th percentile among its peer group of 15,940 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

microsoftpatch availablevia msrc
Product: 18887-16820Fixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: 18757-16823Fixed in: 6.2.0-2
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 x64Fixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 ARMFixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: cm1 qemu-kvm 4.2.0-39 on CBL Mariner 1.0Fixed in: 4.2.0-39
microsoftpatch availablevia msrc
Product: cbl2 qemu 6.2.0-2 on CBL Mariner 2.0Fixed in: 6.2.0-2

Vendor Advisories (3)

microsoft2023-Mar/CVE-2021-3638

CVE-2021-3638

Mar 14, 2023
microsoft2022-Mar/CVE-2021-3638Moderate

An out-of-bounds memory access flaw was found in the ATI VGA device emulation of QEMU. This flaw occurs in the ati_2d_blt() routine while handling MMIO write operations when the guest provides invalid values for the destination display parameters. A malicious guest could use this flaw to crash the QEMU process on the host resulting in a denial of service.

Mar 8, 2022
redhatCVE-2021-3638Low

QEMU: ati-vga: inconsistent check in ati_2d_blt() may lead to out-of-bounds write

Jul 7, 2021

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/GTVPHLLXJ65BUMFBUUZ35F3J632SLFRK
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/I7J5IRXJYLELW7D43A75LOWRUE5EU54O
Mailing ListThird Party Advisory
lists.nongnu.org / archive/html/qemu-devel/2021-09/msg01682.html
ExploitMailing ListPatchThird Party Advisory
security.netapp.com / advisory/ntap-20220407-0003
Third Party Advisory
ubuntu.com / security/CVE-2021-3638
Third Party Advisory