CVE-2021-28715 Denial of service in Linux
A malicious guest can exhaust host kernel memory by bypassing netback driver limits, causing denial of service on the host system.
- 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-2021-28715?
CVE-2021-28715 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 6 Jan 2022. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Guest can force Linux netback driver to hog large amounts of kernel memory T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Incoming data packets for a guest in the Linux kernel's netback driver are buffered until the guest is ready to process them. There are some measures taken for avoiding to pile up too much data, but those can be bypassed by the guest: There is a timeout how long the client side of an interface can stop consuming new packets before it is assumed to have stalled, but this timeout is rather long (60 seconds by default). Using a UDP connection on a fast interface can easily accumulate gigabytes of data in that time. (CVE-2021-28715) The timeout could even never trigger if the guest manages to have only one free slot in its RX queue ring page and the next package would require more than one free slot, which may be the case when using GSO, XDP, or software hashing. (CVE-2021-28714)
Weakness: CWE-770
Which versions are affected by CVE-2021-28715?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2021-28715?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2021-28715 being exploited?
There is no known exploitation of CVE-2021-28715 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as DEBIAN-CVE-2021-28715, GHSA-w6w3-wf72-pc3c, UBUNTU-CVE-2021-28715.