How severe is CVE-2021-20203?

CVE-2021-20203 has a CVSS 3.x base score of 3.2, rated low severity. It is exploitable over local access with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2021-20203 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20203?

CVE-2021-20203 primarily affects Qemu. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20203?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-20203 published?

CVE-2021-20203 was published on 2021-02-25 and last updated on 2026-06-17.

CVE-2021-20203

CVE-2021-20203 is a low-severity vulnerability in Qemu with a CVSS 3.x base score of 3.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

Severity: Low (CVSS 3.x base score 3.2)
CVSS v2: 2.1
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-190
Affected product: Qemu
Published: 2021-02-25
Last modified: 2026-06-17

Description

An integer overflow issue was found in the vmxnet3 NIC emulator of the QEMU for versions up to v5.2.0. It may occur if a guest was to supply invalid values for rx/tx queue size or other NIC parameters. A privileged guest user may use this flaw to crash the QEMU process on the host resulting in DoS scenario.

Frequently asked questions

What is CVE-2021-20203?: An integer overflow issue was found in the vmxnet3 NIC emulator of the QEMU for versions up to v5.2.0. It may occur if a guest was to supply invalid values for rx/tx queue size or other NIC parameters. A privileged guest user may use this flaw to crash the QEMU process on the host resulting in DoS scenario.
How severe is CVE-2021-20203?: CVE-2021-20203 has a CVSS 3.x base score of 3.2, rated low severity. It is exploitable over local access with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2021-20203 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20203?: CVE-2021-20203 primarily affects Qemu. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20203?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20203 published?: CVE-2021-20203 was published on 2021-02-25 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:qemu:qemu:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

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