CVE-2021-28687
First published: Fri Jun 11 2021(Updated: )
HVM soft-reset crashes toolstack libxl requires all data structures passed across its public interface to be initialized before use and disposed of afterwards by calling a specific set of functions. Many internal data structures also require this initialize / dispose discipline, but not all of them. When the "soft reset" feature was implemented, the libxl__domain_suspend_state structure didn't require any initialization or disposal. At some point later, an initialization function was introduced for the structure; but the "soft reset" path wasn't refactored to call the initialization function. When a guest nwo initiates a "soft reboot", uninitialized data structure leads to an assert() when later code finds the structure in an unexpected state. The effect of this is to crash the process monitoring the guest. How this affects the system depends on the structure of the toolstack. For xl, this will have no security-relevant effect: every VM has its own independent monitoring process, which contains no state. The domain in question will hang in a crashed state, but can be destroyed by `xl destroy` just like any other non-cooperating domain. For daemon-based toolstacks linked against libxl, such as libvirt, this will crash the toolstack, losing the state of any in-progress operations (localized DoS), and preventing further administrator operations unless the daemon is configured to restart automatically (system-wide DoS). If crashes "leak" resources, then repeated crashes could use up resources, also causing a system-wide DoS.
Credit: security@xen.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Xen xen-unstable | >=4.12<=4.15.0 | |
| Xen xen-unstable | =4.15.0-rc1 |
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Reference Links
Frequently Asked Questions
What is the severity of CVE-2021-28687?
CVE-2021-28687 has been rated as a high severity vulnerability due to its potential to crash the toolstack of Xen hypervisor.
How do I fix CVE-2021-28687?
To fix CVE-2021-28687, upgrade to the latest version of Xen that addresses this vulnerability.
Which versions of Xen are affected by CVE-2021-28687?
CVE-2021-28687 affects Xen versions 4.12 to 4.15.0 and the 4.15.0-rc1 release.
What type of vulnerability is CVE-2021-28687?
CVE-2021-28687 is a programming error that requires proper initialization and disposal of data structures.
What impact does CVE-2021-28687 have on system stability?
CVE-2021-28687 can lead to a crash of the toolstack, which may disrupt virtual machine management and operations.
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