CVE-2021-28691

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-29 · updated 2026-08-26
Weakness: CWE-416

Description

Guest triggered use-after-free in Linux xen-netback A malicious or buggy network PV frontend can force Linux netback to disable the interface and terminate the receive kernel thread associated with queue 0 in response to the frontend sending a malformed packet. Such kernel thread termination will lead to a use-after-free in Linux netback when the backend is destroyed, as the kernel thread associated with queue 0 will have already exited and thus the call to kthread_stop will be performed against a stale pointer.

Affected products

Linux kernel: from 5.5.0 before 5.10.43 — fixed in 5.10.43
NetApp Cloud Backup: all versions
NetApp H300E Firmware: all versions
NetApp H300S Firmware: all versions
NetApp H410C Firmware: all versions
NetApp H410S Firmware: all versions
NetApp H500E Firmware: all versions
NetApp H500S Firmware: all versions
NetApp H700E Firmware: all versions
NetApp H700S Firmware: all versions
NetApp Solidfire Baseboard Management Controller: all versions

How to fix

Upgrade to a fixed version: Linux kernel 5.10.43. Check the vendor advisory for mitigations.

References

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