How severe is CVE-2021-28688?

CVE-2021-28688 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-28688 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (25th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28688?

CVE-2021-28688 primarily affects Linux Linux Kernel. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-28688?

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

When was CVE-2021-28688 published?

CVE-2021-28688 was published on 2021-04-06 and last updated on 2026-06-17.

CVE-2021-28688

CVE-2021-28688 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 6.5. 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-665.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 2.1
EPSS exploit prediction: 0% (25th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-665
Affected product: Linux Linux Kernel
Published: 2021-04-06
Last modified: 2026-06-17

Description

The fix for XSA-365 includes initialization of pointers such that subsequent cleanup code wouldn't use uninitialized or stale values. This initialization went too far and may under certain conditions also overwrite pointers which are in need of cleaning up. The lack of cleanup would result in leaking persistent grants. The leak in turn would prevent fully cleaning up after a respective guest has died, leaving around zombie domains. All Linux versions having the fix for XSA-365 applied are vulnerable. XSA-365 was classified to affect versions back to at least 3.11.

Frequently asked questions

What is CVE-2021-28688?: The fix for XSA-365 includes initialization of pointers such that subsequent cleanup code wouldn't use uninitialized or stale values. This initialization went too far and may under certain conditions also overwrite pointers which are in need of cleaning up. The lack of cleanup would result in leaking persistent grants. The leak in turn would prevent fully cleaning up after a respective guest has died, leaving around zombie domains. All Linux versions having the fix for XSA-365 applied are vulnerable. XSA-365 was classified to affect versions back to at least 3.11.
How severe is CVE-2021-28688?: CVE-2021-28688 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-28688 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (25th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28688?: CVE-2021-28688 primarily affects Linux Linux Kernel. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-28688?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-28688 published?: CVE-2021-28688 was published on 2021-04-06 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

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