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An issue was discovered in Xen through 4.12.x allowing attackers to gain host OS privileges via DMA in a situation where an untrusted domain has access to a physical device. This occurs because passed through PCI devices may corrupt host memory after deassignment. When a PCI device is assigned to an untrusted domain, it is possible for that domain to program the device to DMA to an arbitrary address. The IOMMU is used to protect the host from malicious DMA by making sure that the device addresses can only target memory assigned to the guest. However, when the guest domain is torn down, or the device is deassigned, the device is assigned back to dom0, thus allowing any in-flight DMA to potentially target critical host data. An untrusted domain with access to a physical device can DMA into host memory, leading to privilege escalation. Only systems where guests are given direct access to physical devices capable of DMA (PCI pass-through) are vulnerable. Systems which do not use PCI pass-through are not vulnerable.

An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be “promoted” before being used as a pagetable, and “demoted” before being used for any other type. Xen also allows for “recursive” promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, and so on. These operations may take an arbitrarily large amount of time, and so must be re-startable. Unfortunately, making recursive pagetable promotion and demotion operations restartable is incredibly complicated, and the code contains several races which, if triggered, can cause Xen to drop or retain extra type counts, potentially allowing guests to get write access to in-use pagetables. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All x86 systems with untrusted PV guests are vulnerable. HVM and PVH guests cannot exercise this vulnerability.

process_http_response in OpenConnect before 8.05 has a Buffer Overflow when a malicious server uses HTTP chunked encoding with crafted chunk sizes.

An issue was discovered in the Linux kernel before 5.1.8. There is a double-free caused by a malicious USB device in the drivers/usb/misc/rio500.c driver.

WriteTIFFImage in coders/tiff.c in ImageMagick 7.0.8-43 Q16 allows attackers to cause a denial-of-service (application crash resulting from a heap-based buffer over-read) via a crafted TIFF image file, related to TIFFRewriteDirectory, TIFFWriteDirectory, TIFFWriteDirectorySec, and TIFFWriteDirectoryTagColormap in tif_dirwrite.c of LibTIFF. NOTE: this occurs because of an incomplete fix for CVE-2019-11597.

drivers/net/wireless/ath/ath6kl/usb.c in the Linux kernel through 5.2.9 has a NULL pointer dereference via an incomplete address in an endpoint descriptor.