CVE-2018-12892 Missing authorization in n/a
Malicious guest administrators can write to read-only SCSI disk images due to a missing readonly flag in libxl, compromising data integrity.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2018-12892?
CVE-2018-12892 is a critical missing authorization vulnerability in Debian Debian Linux, published on 2 Jul 2018. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
An issue was discovered in Xen 4.7 through 4.10.x. libxl fails to pass the readonly flag to qemu when setting up a SCSI disk, due to what was probably an erroneous merge conflict resolution. Malicious guest administrators or (in some situations) users may be able to write to supposedly read-only disk images. Only emulated SCSI disks (specified as "sd" in the libxl disk configuration, or an equivalent) are affected. IDE disks ("hd") are not affected (because attempts to make them readonly are rejected). Additionally, CDROM devices (that is, devices specified to be presented to the guest as CDROMs, regardless of the nature of the backing storage on the host) are not affected; they are always read only. Only systems using qemu-xen (rather than qemu-xen-traditional) as the device model version are vulnerable. Only systems using libxl or libxl-based toolstacks are vulnerable. (This includes xl, and libvirt with the libxl driver.) The vulnerability is present in Xen versions 4.7 and later. (In earlier versions, provided that the patch for XSA-142 has been applied, attempts to create read only disks are rejected.) If the host and guest together usually support PVHVM, the issue is exploitable only if the malicious guest administrator has control of the guest kernel or guest kernel command line.
Weakness: CWE-200
Which versions are affected by CVE-2018-12892?
It affects 2 products.
Products include Debian Debian Linux, Xen Xen.
How do I fix CVE-2018-12892?
Apply the vendor's patch.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2018-12892 being exploited?
There is no known exploitation of CVE-2018-12892 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as ALPINE-CVE-2018-12892, DEBIAN-CVE-2018-12892, GHSA-pv22-mjm8-4f83, UBUNTU-CVE-2018-12892.