CVE-2021-28691 Use after free in Linux
A malicious network frontend can trigger a use-after-free in the Linux kernel netback driver, potentially causing denial of service or code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-28691?
CVE-2021-28691 is a high-severity use after free vulnerability in Linux kernel, published on 29 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-416
Which versions are affected by CVE-2021-28691?
It affects 11 products.
Products include Linux kernel, Netapp Cloud Backup, Netapp H300e Firmware, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware and 5 more.
How do I fix CVE-2021-28691?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2021-28691 being exploited?
There is no known exploitation of CVE-2021-28691 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-6537, DEBIAN-CVE-2021-28691, GHSA-5gvc-4qph-j93r, UBUNTU-CVE-2021-28691.