arch/x86/kvm/x86.c in the Linux kernel before 4.4 does not reset the PIT counter values during state restoration, which allows guest OS users to cause a denial of service (divide-by-zero error and host OS crash) via a zero value, related to the kvm_vm_ioctl_set_pit and kvm_vm_ioctl_set_pit2 functions.

An issue was discovered in the FUSE filesystem implementation in the Linux kernel before 5.10.6, aka CID-5d069dbe8aaf. fuse_do_getattr() calls make_bad_inode() in inappropriate situations, causing a system crash. NOTE: the original fix for this vulnerability was incomplete, and its incompleteness is tracked as CVE-2021-28950.

An issue was discovered in Xen through 4.10.x. Certain PV MMU operations may take a long time to process. For that reason Xen explicitly checks for the need to preempt the current vCPU at certain points. A few rarely taken code paths did bypass such checks. By suitably enforcing the conditions through its own page table contents, a malicious guest may cause such bypasses to be used for an unbounded number of iterations. A malicious or buggy PV guest may cause a Denial of Service (DoS) affecting the entire host. Specifically, it may prevent use of a physical CPU for an indeterminate period of time. All Xen versions from 3.4 onwards are vulnerable. Xen versions 3.3 and earlier are vulnerable to an even wider class of attacks, due to them lacking preemption checks altogether in the affected code paths. Only x86 systems are affected. ARM systems are not affected. Only multi-vCPU x86 PV guests can leverage the vulnerability. x86 HVM or PVH guests as well as x86 single-vCPU PV ones cannot leverage the vulnerability.

The usbvision driver in the Linux kernel package 3.10.0-123.20.1.el7 through 3.10.0-229.14.1.el7 in Red Hat Enterprise Linux (RHEL) 7.1 allows physically proximate attackers to cause a denial of service (panic) via a nonzero bInterfaceNumber value in a USB device descriptor.

Comix 3.6.4 creates temporary directories with predictable names, which allows local users to cause an unspecified denial of service.

Linux kernel 2.6.18, and possibly other versions, when running on AMD64 architectures, allows local users to cause a denial of service (crash) via certain ptrace calls.

fs/direct-io.c in the dio subsystem in the Linux kernel before 2.6.23 does not properly zero out the dio struct, which allows local users to cause a denial of service (OOPS), as demonstrated by a certain fio test.

An issue was discovered in Xen through 4.14.x. Some OSes (such as Linux, FreeBSD, and NetBSD) are processing watch events using a single thread. If the events are received faster than the thread is able to handle, they will get queued. As the queue is unbounded, a guest may be able to trigger an OOM in the backend. All systems with a FreeBSD, Linux, or NetBSD (any version) dom0 are vulnerable.

An issue was discovered in Xen 4.6 through 4.14.x. When acting upon a guest XS_RESET_WATCHES request, not all tracking information is freed. A guest can cause unbounded memory usage in oxenstored. This can lead to a system-wide DoS. Only systems using the Ocaml Xenstored implementation are vulnerable. Systems using the C Xenstored implementation are not vulnerable.

An issue was discovered in drivers/accessibility/speakup/spk_ttyio.c in the Linux kernel through 5.9.9. Local attackers on systems with the speakup driver could cause a local denial of service attack, aka CID-d41227544427. This occurs because of an invalid free when the line discipline is used more than once.

An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the CPU observing consistent state. While the producer side uses appropriately ordered writes, the consumer side isn't protected against re-ordered reads, and may hence end up de-referencing a NULL pointer. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. Only Arm systems may be vulnerable. Whether a system is vulnerable depends on the specific CPU. x86 systems are not vulnerable.

An issue was discovered in Xen through 4.14.x. A guest may access xenstore paths via absolute paths containing a full pathname, or via a relative path, which implicitly includes /local/domain/$DOMID for their own domain id. Management tools must access paths in guests' namespaces, necessarily using absolute paths. oxenstored imposes a pathname limit that is applied solely to the relative or absolute path specified by the client. Therefore, a guest can create paths in its own namespace which are too long for management tools to access. Depending on the toolstack in use, a malicious guest administrator might cause some management tools and debugging operations to fail. For example, a guest administrator can cause "xenstore-ls -r" to fail. However, a guest administrator cannot prevent the host administrator from tearing down the domain. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.

An issue was discovered in Xen through 4.10.x allowing x86 HVM guest OS users to cause a denial of service (host OS infinite loop) in situations where a QEMU device model attempts to make invalid transitions between states of a request.

An issue was discovered in Xen through 4.14.x. When they require assistance from the device model, x86 HVM guests must be temporarily de-scheduled. The device model will signal Xen when it has completed its operation, via an event channel, so that the relevant vCPU is rescheduled. If the device model were to signal Xen without having actually completed the operation, the de-schedule / re-schedule cycle would repeat. If, in addition, Xen is resignalled very quickly, the re-schedule may occur before the de-schedule was fully complete, triggering a shortcut. This potentially repeating process uses ordinary recursive function calls, and thus could result in a stack overflow. A malicious or buggy stubdomain serving a HVM guest can cause Xen to crash, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are affected. Arm systems are not affected. Only x86 stubdomains serving HVM guests can exploit the vulnerability.

The __rds_conn_create function in net/rds/connection.c in the Linux kernel through 4.2.3 allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact by using a socket that was not properly bound.

An issue was discovered in Xen through 4.14.x. When a Xenstore watch fires, the xenstore client that registered the watch will receive a Xenstore message containing the path of the modified Xenstore entry that triggered the watch, and the tag that was specified when registering the watch. Any communication with xenstored is done via Xenstore messages, consisting of a message header and the payload. The payload length is limited to 4096 bytes. Any request to xenstored resulting in a response with a payload longer than 4096 bytes will result in an error. When registering a watch, the payload length limit applies to the combined length of the watched path and the specified tag. Because watches for a specific path are also triggered for all nodes below that path, the payload of a watch event message can be longer than the payload needed to register the watch. A malicious guest that registers a watch using a very large tag (i.e., with a registration operation payload length close to the 4096 byte limit) can cause the generation of watch events with a payload length larger than 4096 bytes, by writing to Xenstore entries below the watched path. This will result in an error condition in xenstored. This error can result in a NULL pointer dereference, leading to a crash of xenstored. A malicious guest administrator can cause xenstored to crash, leading to a denial of service. Following a xenstored crash, domains may continue to run, but management operations will be impossible. Only C xenstored is affected, oxenstored is not affected.

An issue was discovered in the Linux kernel through 5.9.1, as used with Xen through 4.14.x. Guest OS users can cause a denial of service (host OS hang) via a high rate of events to dom0, aka CID-e99502f76271.

A divide-by-zero issue was found in dwc2_handle_packet in hw/usb/hcd-dwc2.c in the hcd-dwc2 USB host controller emulation of QEMU. A malicious guest could use this flaw to crash the QEMU process on the host, resulting in a denial of service.

Linux kernel before version 4.16-rc7 is vulnerable to a null pointer dereference in dccp_write_xmit() function in net/dccp/output.c in that allows a local user to cause a denial of service by a number of certain crafted system calls.

A flaw was found in the Linux kernel's ext4 filesystem. A local user can cause an out-of-bound access in ext4_get_group_info function, a denial of service, and a system crash by mounting and operating on a crafted ext4 filesystem image.

Red Hat Enterprise Linux 5 and Fedora install the Bind /etc/rndc.key file with world-readable permissions, which allows local users to perform unauthorized named commands, such as causing a denial of service by stopping named.

A flaw was found in Linux kernel in the ext4 filesystem code. A use-after-free is possible in ext4_ext_remove_space() function when mounting and operating a crafted ext4 image.

A NULL pointer dereference flaw was found in the Linux kernel's GPU Nouveau driver functionality in versions prior to 5.12-rc1 in the way the user calls ioctl DRM_IOCTL_NOUVEAU_CHANNEL_ALLOC. This flaw allows a local user to crash the system.

An issue was discovered in Xen through 4.14.x. Out of bounds event channels are available to 32-bit x86 domains. The so called 2-level event channel model imposes different limits on the number of usable event channels for 32-bit x86 domains vs 64-bit or Arm (either bitness) ones. 32-bit x86 domains can use only 1023 channels, due to limited space in their shared (between guest and Xen) information structure, whereas all other domains can use up to 4095 in this model. The recording of the respective limit during domain initialization, however, has occurred at a time where domains are still deemed to be 64-bit ones, prior to actually honoring respective domain properties. At the point domains get recognized as 32-bit ones, the limit didn't get updated accordingly. Due to this misbehavior in Xen, 32-bit domains (including Domain 0) servicing other domains may observe event channel allocations to succeed when they should really fail. Subsequent use of such event channels would then possibly lead to corruption of other parts of the shared info structure. An unprivileged guest may cause another domain, in particular Domain 0, to misbehave. This may lead to a Denial of Service (DoS) for the entire system. All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable. Only x86 32-bit domains servicing other domains are vulnerable. Arm systems, as well as x86 64-bit domains, are not vulnerable.

A flaw memory leak in the Linux kernel performance monitoring subsystem was found in the way if using PERF_EVENT_IOC_SET_FILTER. A local user could use this flaw to starve the resources causing denial of service.

The KVM subsystem in the Linux kernel through 4.2.6, and Xen 4.3.x through 4.6.x, allows guest OS users to cause a denial of service (host OS panic or hang) by triggering many #AC (aka Alignment Check) exceptions, related to svm.c and vmx.c.

An issue was discovered in Xen through 4.14.x. There is a lack of preemption in evtchn_reset() / evtchn_destroy(). In particular, the FIFO event channel model allows guests to have a large number of event channels active at a time. Closing all of these (when resetting all event channels or when cleaning up after the guest) may take extended periods of time. So far, there was no arrangement for preemption at suitable intervals, allowing a CPU to spend an almost unbounded amount of time in the processing of these operations. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. All Xen versions are vulnerable in principle. Whether versions 4.3 and older are vulnerable depends on underlying hardware characteristics.

Memory leak in the Red Hat Content Accelerator kernel patch in Red Hat Enterprise Linux (RHEL) 4 and 5 allows local users to cause a denial of service (memory consumption) via a large number of open requests involving O_ATOMICLOOKUP.

Linux kernel before 2.4.21 allows local users to cause a denial of service (kernel panic) via asynchronous input or output on a FIFO special file.

The Linux Kernel version 3.18 contains a dangerous feature vulnerability in modify_user_hw_breakpoint() that can result in crash and possibly memory corruption. This attack appear to be exploitable via local code execution and the ability to use ptrace. This vulnerability appears to have been fixed in git commit f67b15037a7a50c57f72e69a6d59941ad90a0f0f.

The xfs_bmap_extents_to_btree function in fs/xfs/libxfs/xfs_bmap.c in the Linux kernel through 4.16.3 allows local users to cause a denial of service (xfs_bmapi_write NULL pointer dereference) via a crafted xfs image.

A flaw was found in the Linux kernel's implementation of biovecs in versions before 5.9-rc7. A zero-length biovec request issued by the block subsystem could cause the kernel to enter an infinite loop, causing a denial of service. This flaw allows a local attacker with basic privileges to issue requests to a block device, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

An issue was discovered in Xen through 4.11.x. ARM never properly implemented grant table v2, either in the hypervisor or in Linux. Unfortunately, an ARM guest can still request v2 grant tables; they will simply not be properly set up, resulting in subsequent grant-related hypercalls hitting BUG() checks. An unprivileged guest can cause a BUG() check in the hypervisor, resulting in a denial-of-service (crash).

The Linux kernel before 4.15-rc8 was found to be vulnerable to a NULL pointer dereference bug in the __netlink_ns_capable() function in the net/netlink/af_netlink.c file. A local attacker could exploit this when a net namespace with a netnsid is assigned to cause a kernel panic and a denial of service.

Memory leak in the virtio_gpu_set_scanout function in hw/display/virtio-gpu.c in QEMU (aka Quick Emulator) allows local guest OS users to cause a denial of service (memory consumption) via a large number of "VIRTIO_GPU_CMD_SET_SCANOUT:" commands.

hw/scsi/vmw_pvscsi.c in QEMU (aka Quick Emulator) allows local guest OS privileged users to cause a denial of service (infinite loop and CPU consumption) via the message ring page count.

The ping_unhash function in net/ipv4/ping.c in the Linux kernel before 4.0.3 does not initialize a certain list data structure during an unhash operation, which allows local users to gain privileges or cause a denial of service (use-after-free and system crash) by leveraging the ability to make a SOCK_DGRAM socket system call for the IPPROTO_ICMP or IPPROTO_ICMPV6 protocol, and then making a connect system call after a disconnect.

A use after free vulnerability in ip_reass() in ip_input.c of libslirp 4.2.0 and prior releases allows crafted packets to cause a denial of service.

A certain backport in the TCP Fast Open implementation for the Linux kernel before 3.18 does not properly maintain a count value, which allow local users to cause a denial of service (system crash) via the Fast Open feature, as demonstrated by visiting the chrome://flags/#enable-tcp-fast-open URL when using certain 3.10.x through 3.16.x kernel builds, including longterm-maintenance releases and ckt (aka Canonical Kernel Team) builds.

Improper invalidation for page table updates by a virtual guest operating system for multiple Intel(R) Processors may allow an authenticated user to potentially enable denial of service of the host system via local access.