paravirtualised kernel image validation

ISSUE DESCRIPTION 1. Problems ----------- The functions which interpret the kernel image supplied for a paravirtualised guest, and decompress it into memory when booting the domain, are incautious. Specifically: i Integer overflow in the decompression loop memory allocator might result in...

x86: CPU Opcode Cache corruption

ISSUE DESCRIPTION AMD have disclosed a potential vulnerability in certain CPUs which can cause instructions to execute at a higher privilege. For more information, see: https://www.amd.com/en/resources/product-security/bulletin/amd-sb-7052.html IMPACT Code of any privilege could escalate to a...

oxenstored keeps quota related use counts across domain destruction

ISSUE DESCRIPTION When oxenstored is tearing a domain down, the node data is cleaned up but the usage counts are leaked. When the domain ID is eventually reused, the new domain can create fewer nodes before beeing deemed to be over quota. IMPACT Over an extended period of time, new domains will b...

Incorrect removal of permissions on PCI device unplug

ISSUE DESCRIPTION When passing through PCI devices, the detach logic in libxl won't remove access permissions to any 64bit memory BARs the device might have. As a result a domain can still have access any 64bit memory BAR when such device is no longer assigned to the domain. For PV domains the...

Arm issues with page refcounting

ISSUE DESCRIPTION There are two issues related to the mapping of pages belonging to other domains: For one, an assertion is wrong there, where the case actually needs handling. A NULL pointer de-reference could result on a release build. This is CVE-2025-58144. And then the P2M lock isn't held...

x86: Incorrect stubs exception handling for flags recovery

ISSUE DESCRIPTION Certain instructions need intercepting and emulating by Xen. In some cases Xen emulates the instruction by replaying it, using an executable stub. Some instructions may raise an exception, which is supposed to be handled gracefully. Certain replayed instructions have additional...

frontends vulnerable to backends

ISSUE DESCRIPTION Xen offers the ability to run PV backends in regular unprivileged guests, typically referred to as "driver domains". Running PV backends in driver domains has one primary security advantage: if a driver domain gets compromised, it doesn't have the privileges to take over the...

WITHDRAWN: missing XSETBV intercept privilege check on AMD SVM

ISSUE DESCRIPTION NOTE: This advisory has been withdrawn XSETBV is a privileged instruction, i.e. should result in GP when issued by code running at other than the most privileged level CPL 0. Unlike other privileged and intercepted instructions in AMD SVM, XSETBV has the privilege level check do...

hypercall physdev_get_free_pirq vulnerability

ISSUE DESCRIPTION PHYSDEVOPgetfreepirq does not check that its call to getfreepirq succeeded, and if it fails will use the error code as an array index. IMPACT A malicious guest might be able to cause the host to crash, leading to a DoS, depending on the exact memory layout. Privilege escalation ...

HVM guest user mode MMIO emulation DoS vulnerability

ISSUE DESCRIPTION Internal data of the emulator for MMIO operations may, under certain rare conditions, at the end of one emulation cycle be left in a state affecting a subsequent emulation such that this second emulation would fail, causing an exception to be reported to the guest kernel where...

qemu-dm Local Privilege Escalation Vulnerability

ISSUE DESCRIPTION Heap-based buffer overflow in the processtxdesc function in the e1000 emulation allows the guest to cause a denial of service QEMU crash and possibly execute arbitrary code via crafted legacy mode packets. Upstream qemu has already released an advisory hence there is no embargo...

Xen <= 3.3 DoS due to incorrect virtual address validation

ISSUE DESCRIPTION The x8664 addrok macro intends to ensure that the checked address is either in the positive half of the 48-bit virtual address space, or above the Xen-reserved area. However, the current shift count is off-by-one, allowing full access to the "negative half" too, via certain...

vNUMA domain cleanup may race other operations

ISSUE DESCRIPTION Accessing the vNUMA configuration data of a guest is still possible when domain destruction has already started. The cleaning up of that configuration information is not synchronized with its retrieval by a device model controlling the guest. IMPACT While Denial of Service DoS...

XAPI: Missing TLS verification in some SDKs

ISSUE DESCRIPTION XAPI provides SDKs; bindings for the API in various programming languages. These are artefacts from a build of XAPI, intended for integration into 3rd party products. In all SDKs, there is a main RPC connection to the XAPI host. TLS for this connection is verified properly, or...

Xenstored DoS by unprivileged domain

ISSUE DESCRIPTION Any guest issuing a Xenstore command accessing a node using the illegal node path "/local/domain/", will crash xenstored due to a clobbered error indicator in xenstored when verifying the node path. Note that the crash is forced via a failing assert statement in xenstored. In ca...

XAPI UTF-8 string handling

ISSUE DESCRIPTION There are multiple issues. 1. Updates to the XAPI database sanitise input strings, but try generating the notification using the unsanitised input. This causes the database's event thread to terminate and cease further processing. 2. XAPI's UTF-8 encoder implements v3.0 of the...

virtual PMU is unsupported

ISSUE DESCRIPTION The Virtual Performance Measurement Unit feature has been documented as unsupported, so far only on Intel CPUs. Further issues have been found or are suspected which would also or exclusively affect AMD CPUs. We believe that the functionality is mostly intended for non-productio...

grant table entry swaps have inadequate bounds checking

ISSUE DESCRIPTION The grant table hypercall's GNTTABOPswapgrantref sub-operation does not perform adequate checks on the input grant references. IMPACT A malicious guest kernel or administrator can crash the host. It may be possible for an attacker to swap a valid grant reference, which they...

hypercall set_debugreg vulnerability

ISSUE DESCRIPTION setdebugreg allows writes to reserved bits of the DR7 debug control register on x86-64. IMPACT A malicious guest can cause the host to crash, leading to a DoS. If the vulnerable hypervisor is run on future hardware, the impact of the vulnerability might be widened depending on t...

HVM guest destroy p2m teardown host DoS vulnerability

ISSUE DESCRIPTION An HVM guest is able to manipulate its physical address space such that tearing down the guest takes an extended period amount of time searching for shared pages. This causes the domain 0 VCPU which tears down the domain to be blocked in the destroy hypercall. This causes that...

grant-table: type confusion in grant-copy

ISSUE DESCRIPTION When grant-copy operations are processed, the respective grant may or may not already be in use by another operation a mapping or another copy. For all copy operations the referenced guest frame is looked up. When another operation is already active for the grant the grant is...

x86: Floating Point Divider State Sampling

ISSUE DESCRIPTION Researchers from the CISPA Helmholtz Center for Information Security have discovered Floating Point Divider State Sampling. It is detailed in a paper titled "TREVEX: A Black-Box Detection Framework For Data-Flow Transient Execution Vulnerabilities" For more information, see:...

x86: buffer overrun with shadow paging + tracing

ISSUE DESCRIPTION Shadow mode tracing code uses a set of per-CPU variables to avoid cumbersome parameter passing. Some of these variables are written to with guest controlled data, of guest controllable size. That size can be larger than the variable, and bounding of the writes was missing. IMPAC...

guest denial of service on syscall/sysenter exception generation

ISSUE DESCRIPTION When guest user code running inside a Xen guest operating system attempts to execute a syscall or sysenter instruction, but when the guest operating system has not registered a handler for that instruction, a General Protection Fault may need to be injected into the guest. It ha...

Timer overflow DoS vulnerability

ISSUE DESCRIPTION A guest which sets a VCPU with an inappropriate deadline can cause an infinite loop in Xen, blocking the affected physical CPU indefinitely. IMPACT A malicious guest administrator can trigger the bug. If the Xen watchdog is enabled, the whole system will crash. Otherwise the gue...

guest administrator can access qemu monitor console

ISSUE DESCRIPTION A guest administrator who is granted access to the graphical console of a Xen guest can access the qemu monitor. The monitor can be used to access host resources. IMPACT A malicious guest administrator can access host resources perhaps belonging to other guests or the underlying...

PHYSDEVOP_map_pirq index vulnerability

ISSUE DESCRIPTION PHYSDEVOPmappirq with MAPPIRQTYPEGSI does not range check map-index. IMPACT A malicious HVM guest kernel can crash the host. It might also be able to read hypervisor or guest memory. VULNERABLE SYSTEMS All Xen systems running HVM guests. PV guests are not vulnerable. The...

VT-d (PCI passthrough) MSI trap injection

ISSUE DESCRIPTION Intel VT-d chipsets without interrupt remapping do not prevent a guest which owns a PCI device from using DMA to generate MSI interrupts by writing to the interrupt injection registers. This can be exploited to inject traps and gain control of the host. VULNERABLE SYSTEMS You ar...

Linux kernel out of bounds read via Xen-related sysfs file

ISSUE DESCRIPTION The Linux sysfs file /sys/hypervisor/properties/buildid does not contain printable information, but a binary value of typically 16 or 20 bytes, which is not terminated by a zero byte. The kernel driver making this information available is using the sprintf function for writing t...

Unhooking empty PAE entries DoS vulnerability

ISSUE DESCRIPTION The HVMOPpagetabledying hypercall does not correctly check the caller's pagetable state, leading to a hypervisor crash. IMPACT An HVM guest running on shadow pagetables that is, not HAP can cause the hypervisor to crash. VULNERABLE SYSTEMS All Xen versions from 4.0 onwards are...

x86 shadow paging is deprecated

ISSUE DESCRIPTION Addressing certain issues, in particular related to operations which may take excessively long and therefore would need preemption, has turned out overly costly. Since alternatives HVM/PVH: HAP, PV: shim are commonly available, the decision was to deprecate the functionality,...

Xenstored DoS via XS_RESET_WATCHES command

ISSUE DESCRIPTION Any guest can cause xenstored to crash by issuing a XSRESETWATCHES command within a transaction due to an assert triggering. In case xenstored was built with NDEBUG defined nothing bad will happen, as assert is doing nothing in this case. Note that the default is not to define...

PV guest host Denial of Service

ISSUE DESCRIPTION A Xen user has discovered that some older AMD CPUs can be made to lock up due to AMD processor erratum 121. This issue was discovered during testing of the fix for XSA-7 CVE-2012-0217. Although the two issues are unrelated the situations which can trigger them may overlap...

64-bit PV guest privilege escalation vulnerability

ISSUE DESCRIPTION Rafal Wojtczuk has discovered a vulnerability which can allow a 64-bit PV guest kernel running on a 64-bit hypervisor to escalate privileges to that of the host by arranging for a system call to return via sysret to a non-canonical RIP. Intel CPUs deliver the resulting exception...

PoD: Don't try to reclaim special pages

ISSUE DESCRIPTION A guest started with Populated on Demand enabled PoD can attempt to reclaim pages which aren't regular guest RAM. This can cause corruption of memory management state in Xen. IMPACT A buggy or malicious guest can cause corruption of Xen's state, leading to crashes or other...

sysctl and platform-op locks open to abuse

ISSUE DESCRIPTION To manage the system, sysctl and platform operations are used by the control domain or a possible Xenstore domain. Some of these operations may not be executed in parallel, so a system-wide lock each is used. The way those locks are acquired is, however, not providing any...

Non-standard PCI device functionality may render pass-through insecure

ISSUE DESCRIPTION Devices with capabilities or defects that are undocumented or that virtualization software is unaware of may allow guests to control parts of the host that they shouldn't be in control of. Here are some examples of the kind of problem: While XSA-120 deals with standard PCI confi...

Qemu VT100 emulation vulnerability

ISSUE DESCRIPTION The device model used by fully virtualised HVM domains, qemu, does not properly handle escape VT100 sequences when emulating certain devices with a virtual console backend. IMPACT An attacker who has sufficient privilege to access a vulnerable device within a guest can overwrite...

Host crash due to failure to correctly validate PV kernel execution state

ISSUE DESCRIPTION Cannot specify user mode execution without specifying user-mode pagetables. Failure to validate this allows a malicious or buggy 64 bit PV guest to crash the host. nb: predates vulnerability handling process and therefore no formal announcement...

correct buffer checks for DM_OP hypercalls

ISSUE DESCRIPTION Parts of the DMOP handling code assumes the caller has provided the required number of buffers for the given operation without any checking being done. As a result, certain operations might access stack rubble as structures are possibly uninitialized. IMPACT A device model of a...

x86: Incorrect input sanitisation in Viridian hypercalls

ISSUE DESCRIPTION Some Viridian hypercalls can specify a mask of vCPU IDs as an input, in one of three formats. Xen has boundary checking bugs with all three formats, which can cause out-of-bounds reads and writes while processing the inputs. CVE-2025-58147. Hypercalls using the HVVPSET Sparse...

Disaggregated domain management security status

ISSUE DESCRIPTION Xen supports disaggregation of various support and management functions into their own domains; this is often done for security and robustness reasons. In Xen 4.3 additional functionality was introduced to allow further disaggregation: the Xen Security Modules mechanism was...

x86: Out-of-bounds read in vRTC emulation

ISSUE DESCRIPTION Accesses to the CMOS memory contents are done using an indirect IO port pair. Therefore Xen needs to cache the guest chosen index, and one of the usages of the index didn't take the necessary locking to avoid concurrent changes. As a result, a guest could change the index after ...

buffer overruns in libfsimage iso9660 handling

ISSUE DESCRIPTION The directory and Rock Ridge / SUSP walk in libfsimage's iso9660 driver derives several lengths directly from attacker-controlled on-disk fields without validating them: The directory loop itself assumes a good record length. This is CVE-2026-42494. The calculation of the System...

vIRQ event channel binding may break Xenstore

ISSUE DESCRIPTION Xenstore, to have an up-to-date picture of the entire system, wants to know of domains appearing and disappearing. To make this more robust, a new XENDOMCTLgetdomainstate was introduced. The management of the bitmap underlying that operation is tied into the binding of the...

evtchn: Race between FIFO expand and reset

ISSUE DESCRIPTION The EVTCHNOPexpandarray hypercall checks for whether FIFO event channels are enabled, but without holding the correct lock. It can race with EVTCHNOPreset, resulting in dereferencing a NULL pointer. IMPACT A malicious HVM guest x86 HVM or PVH, and ARM can crash Xen leading to a...

Unconditionally do TLB flushing ahead of page scrubbing

ISSUE DESCRIPTION x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen if needed when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify ...

oxenstored: Unbounded accumulation of watches

ISSUE DESCRIPTION Oxenstored maintains two datastructures about watches; one global trie, and one hashtable tracked per domain. When a xenbus reconnect is requested, watches are not cleared out of the global trie. IMPACT A guest can cause unbounded memory usage in oxenstored. This can lead to a...

Withdrawn Xen Security Advisory number

DESCRIPTION XSA-283 stated: VT-d: Incorrect accesses into the Interrupt Remapping table A VT-d IOMMU has several tables in main RAM, which are configured by the driver when it starts. The tables are required to be aligned on a 4k boundary, and the control registers in the IOMMU which point to the...

Out-of-bounds accesses in Tapdisk

ISSUE DESCRIPTION Tapdisk is a userspace xen-blkback implementation used by the XAPI toolstack. Several bounds checks have been found to be incorrect. There is no upper bounds check for blkif-lastsect. Passing a value larger than 7 will result in a read or write beyond the mapped grant. This is...