x86 shadow paging arbitrary pointer dereference In environments where host assisted address translation is necessary but Hardware Assisted Paging (HAP) is unavailable, Xen will run guests in so called shadow mode. Due to too lax a check in one of the hypervisor routines used for shadow page handling it is possible for a guest with a PCI device passed through to cause the hypervisor to access an arbitrary pointer partially under guest control.

The remote host is affected by the vulnerability described in GLSA-202402-07 (Xen: Multiple Vulnerabilities)

  - grant table v2 status pages may remain accessible after de-allocation (take two) Guest get permitted     access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with     a guest for its entire lifetime. Grant table v2 status pages, however, get de-allocated when a guest     switched (back) from v2 to v1. The freeing of such pages requires that the hypervisor know where in the     guest these pages were mapped. The hypervisor tracks only one use within guest space, but racing requests     from the guest to insert mappings of these pages may result in any of them to become mapped in multiple     locations. Upon switching back from v2 to v1, the guest would then retain access to a page that was freed     and perhaps re-used for other purposes. This bug was fortuitously fixed by code cleanup in Xen 4.14, and     backported to security-supported Xen branches as a prerequisite of the fix for XSA-378. (CVE-2021-28703)

  - PoD operations on misaligned GFNs T[his CNA information record relates to multiple CVEs; the text explains     which aspects/vulnerabilities correspond to which CVE.] x86 HVM and PVH guests may be started in populate-     on-demand (PoD) mode, to provide a way for them to later easily have more memory assigned. Guests are     permitted to control certain P2M aspects of individual pages via hypercalls. These hypercalls may act on     ranges of pages specified via page orders (resulting in a power-of-2 number of pages). The implementation     of some of these hypercalls for PoD does not enforce the base page frame number to be suitably aligned for     the specified order, yet some code involved in PoD handling actually makes such an assumption. These     operations are XENMEM_decrease_reservation (CVE-2021-28704) and XENMEM_populate_physmap (CVE-2021-28707),     the latter usable only by domains controlling the guest, i.e. a de-privileged qemu or a stub domain.
    (Patch 1, combining the fix to both these two issues.) In addition handling of XENMEM_decrease_reservation     can also trigger a host crash when the specified page order is neither 4k nor 2M nor 1G (CVE-2021-28708,     patch 2). (CVE-2021-28704, CVE-2021-28707, CVE-2021-28708)

  - issues with partially successful P2M updates on x86 T[his CNA information record relates to multiple CVEs;
    the text explains which aspects/vulnerabilities correspond to which CVE.] x86 HVM and PVH guests may be     started in populate-on-demand (PoD) mode, to provide a way for them to later easily have more memory     assigned. Guests are permitted to control certain P2M aspects of individual pages via hypercalls. These     hypercalls may act on ranges of pages specified via page orders (resulting in a power-of-2 number of     pages). In some cases the hypervisor carries out the requests by splitting them into smaller chunks. Error     handling in certain PoD cases has been insufficient in that in particular partial success of some     operations was not properly accounted for. There are two code paths affected - page removal     (CVE-2021-28705) and insertion of new pages (CVE-2021-28709). (We provide one patch which combines the fix     to both issues.) (CVE-2021-28705, CVE-2021-28709)

  - guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of     memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator     established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It     would then only be the overflowed (and hence small) number which gets compared against the established     upper bound. (CVE-2021-28706)

  - Rejected reason: DO NOT USE THIS CANDIDATE NUMBER. ConsultIDs: none. Reason: This candidate is unused by     its CNA. Notes: none. (CVE-2022-23816)

  - IBPB may not prevent return branch predictions from being specified by pre-IBPB branch targets leading to     a potential information disclosure. (CVE-2022-23824)

  - Aliases in the branch predictor may cause some AMD processors to predict the wrong branch type potentially     leading to information disclosure. (CVE-2022-23825)

  - Racy interactions between dirty vram tracking and paging log dirty hypercalls Activation of log dirty mode     done by XEN_DMOP_track_dirty_vram (was named HVMOP_track_dirty_vram before Xen 4.9) is racy with ongoing     log dirty hypercalls. A suitably timed call to XEN_DMOP_track_dirty_vram can enable log dirty while     another CPU is still in the process of tearing down the structures related to a previously enabled log     dirty mode (XEN_DOMCTL_SHADOW_OP_OFF). This is due to lack of mutually exclusive locking between both     operations and can lead to entries being added in already freed slots, resulting in a memory leak.
    (CVE-2022-26356)

  - race in VT-d domain ID cleanup Xen domain IDs are up to 15 bits wide. VT-d hardware may allow for only     less than 15 bits to hold a domain ID associating a physical device with a particular domain. Therefore     internally Xen domain IDs are mapped to the smaller value range. The cleaning up of the housekeeping     structures has a race, allowing for VT-d domain IDs to be leaked and flushes to be bypassed.
    (CVE-2022-26357)

  - IOMMU: RMRR (VT-d) and unity map (AMD-Vi) handling issues T[his CNA information record relates to multiple     CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Certain PCI devices in a     system might be assigned Reserved Memory Regions (specified via Reserved Memory Region Reporting, RMRR)     for Intel VT-d or Unity Mapping ranges for AMD-Vi. These are typically used for platform tasks such as     legacy USB emulation. Since the precise purpose of these regions is unknown, once a device associated with     such a region is active, the mappings of these regions need to remain continuouly accessible by the     device. This requirement has been violated. Subsequent DMA or interrupts from the device may have     unpredictable behaviour, ranging from IOMMU faults to memory corruption. (CVE-2022-26358, CVE-2022-26359,     CVE-2022-26360, CVE-2022-26361)

  - When SMT is enabled, certain AMD processors may speculatively execute instructions using a target from the     sibling thread after an SMT mode switch potentially resulting in information disclosure. (CVE-2022-27672)

  - Mis-trained branch predictions for return instructions may allow arbitrary speculative code execution     under certain microarchitecture-dependent conditions. (CVE-2022-29900)

  - Intel microprocessor generations 6 to 8 are affected by a new Spectre variant that is able to bypass their     retpoline mitigation in the kernel to leak arbitrary data. An attacker with unprivileged user access can     hijack return instructions to achieve arbitrary speculative code execution under certain     microarchitecture-dependent conditions. (CVE-2022-29901)

  - P2M pool freeing may take excessively long The P2M pool backing second level address translation for     guests may be of significant size. Therefore its freeing may take more time than is reasonable without     intermediate preemption checks. Such checking for the need to preempt was so far missing. (CVE-2022-33746)

  - Arm: unbounded memory consumption for 2nd-level page tables Certain actions require e.g. removing pages     from a guest's P2M (Physical-to-Machine) mapping. When large pages are in use to map guest pages in the     2nd-stage page tables, such a removal operation may incur a memory allocation (to replace a large mapping     with individual smaller ones). These memory allocations are taken from the global memory pool. A malicious     guest might be able to cause the global memory pool to be exhausted by manipulating its own P2M mappings.
    (CVE-2022-33747)

  - lock order inversion in transitive grant copy handling As part of XSA-226 a missing cleanup call was     inserted on an error handling path. While doing so, locking requirements were not paid attention to. As a     result two cooperating guests granting each other transitive grants can cause locks to be acquired nested     within one another, but in respectively opposite order. With suitable timing between the involved grant     copy operations this may result in the locking up of a CPU. (CVE-2022-33748)

  - XAPI open file limit DoS It is possible for an unauthenticated client on the network to cause XAPI to hit     its file-descriptor limit. This causes XAPI to be unable to accept new requests for other (trusted)     clients, and blocks XAPI from carrying out any tasks that require the opening of file descriptors.
    (CVE-2022-33749)

  - Xenstore: Guests can crash xenstored Due to a bug in the fix of XSA-115 a malicious guest can cause     xenstored to use a wrong pointer during node creation in an error path, resulting in a crash of xenstored     or a memory corruption in xenstored causing further damage. Entering the error path can be controlled by     the guest e.g. by exceeding the quota value of maximum nodes per domain. (CVE-2022-42309)

  - Xenstore: Guests can create orphaned Xenstore nodes By creating multiple nodes inside a transaction     resulting in an error, a malicious guest can create orphaned nodes in the Xenstore data base, as the     cleanup after the error will not remove all nodes already created. When the transaction is committed after     this situation, nodes without a valid parent can be made permanent in the data base. (CVE-2022-42310)

  - Xenstore: Guests can cause Xenstore to not free temporary memory When working on a request of a guest,     xenstored might need to allocate quite large amounts of memory temporarily. This memory is freed only     after the request has been finished completely. A request is regarded to be finished only after the guest     has read the response message of the request from the ring page. Thus a guest not reading the response can     cause xenstored to not free the temporary memory. This can result in memory shortages causing Denial of     Service (DoS) of xenstored. (CVE-2022-42319)

  - Xenstore: Guests can get access to Xenstore nodes of deleted domains Access rights of Xenstore nodes are     per domid. When a domain is gone, there might be Xenstore nodes left with access rights containing the     domid of the removed domain. This is normally no problem, as those access right entries will be corrected     when such a node is written later. There is a small time window when a new domain is created, where the     access rights of a past domain with the same domid as the new one will be regarded to be still valid,     leading to the new domain being able to get access to a node which was meant to be accessible by the     removed domain. For this to happen another domain needs to write the node before the newly created domain     is being introduced to Xenstore by dom0. (CVE-2022-42320)

  - Xenstore: Guests can crash xenstored via exhausting the stack Xenstored is using recursion for some     Xenstore operations (e.g. for deleting a sub-tree of Xenstore nodes). With sufficiently deep nesting     levels this can result in stack exhaustion on xenstored, leading to a crash of xenstored. (CVE-2022-42321)

  - Xenstore: Cooperating guests can create arbitrary numbers of nodes T[his CNA information record relates to     multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Since the fix of     XSA-322 any Xenstore node owned by a removed domain will be modified to be owned by Dom0. This will allow     two malicious guests working together to create an arbitrary number of Xenstore nodes. This is possible by     domain A letting domain B write into domain A's local Xenstore tree. Domain B can then create many nodes     and reboot. The nodes created by domain B will now be owned by Dom0. By repeating this process over and     over again an arbitrary number of nodes can be created, as Dom0's number of nodes isn't limited by     Xenstore quota. (CVE-2022-42322, CVE-2022-42323)

  - Oxenstored 32->31 bit integer truncation issues Integers in Ocaml are 63 or 31 bits of signed precision.
    The Ocaml Xenbus library takes a C uint32_t out of the ring and casts it directly to an Ocaml integer. In     64-bit Ocaml builds this is fine, but in 32-bit builds, it truncates off the most significant bit, and     then creates unsigned/signed confusion in the remainder. This in turn can feed a negative value into logic     not expecting a negative value, resulting in unexpected exceptions being thrown. The unexpected exception     is not handled suitably, creating a busy-loop trying (and failing) to take the bad packet out of the     xenstore ring. (CVE-2022-42324)

  - Xenstore: Guests can create arbitrary number of nodes via transactions T[his CNA information record     relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] In     case a node has been created in a transaction and it is later deleted in the same transaction, the     transaction will be terminated with an error. As this error is encountered only when handling the deleted     node at transaction finalization, the transaction will have been performed partially and without updating     the accounting information. This will enable a malicious guest to create arbitrary number of nodes.
    (CVE-2022-42325, CVE-2022-42326)

  - x86: unintended memory sharing between guests On Intel systems that support the virtualize APIC accesses     feature, a guest can read and write the global shared xAPIC page by moving the local APIC out of xAPIC     mode. Access to this shared page bypasses the expected isolation that should exist between two guests.
    (CVE-2022-42327)

  - Guests can cause Xenstore crash via soft reset When a guest issues a Soft Reset (e.g. for performing a     kexec) the libxl based Xen toolstack will normally perform a XS_RELEASE Xenstore operation. Due to a bug     in xenstored this can result in a crash of xenstored. Any other use of XS_RELEASE will have the same     impact. (CVE-2022-42330)

  - x86: speculative vulnerability in 32bit SYSCALL path Due to an oversight in the very original     Spectre/Meltdown security work (XSA-254), one entrypath performs its speculation-safety actions too late.
    In some configurations, there is an unprotected RET instruction which can be attacked with a variety of     speculative attacks. (CVE-2022-42331)

  - x86 shadow plus log-dirty mode use-after-free In environments where host assisted address translation is     necessary but Hardware Assisted Paging (HAP) is unavailable, Xen will run guests in so called shadow mode.
    Shadow mode maintains a pool of memory used for both shadow page tables as well as auxiliary data     structures. To migrate or snapshot guests, Xen additionally runs them in so called log-dirty mode. The     data structures needed by the log-dirty tracking are part of aformentioned auxiliary data. In order to     keep error handling efforts within reasonable bounds, for operations which may require memory allocations     shadow mode logic ensures up front that enough memory is available for the worst case requirements.
    Unfortunately, while page table memory is properly accounted for on the code path requiring the potential     establishing of new shadows, demands by the log-dirty infrastructure were not taken into consideration. As     a result, just established shadow page tables could be freed again immediately, while other code is still     accessing them on the assumption that they would remain allocated. (CVE-2022-42332)

  - x86/HVM pinned cache attributes mis-handling T[his CNA information record relates to multiple CVEs; the     text explains which aspects/vulnerabilities correspond to which CVE.] To allow cachability control for HVM     guests with passed through devices, an interface exists to explicitly override defaults which would     otherwise be put in place. While not exposed to the affected guests themselves, the interface specifically     exists for domains controlling such guests. This interface may therefore be used by not fully privileged     entities, e.g. qemu running deprivileged in Dom0 or qemu running in a so called stub-domain. With this     exposure it is an issue that - the number of the such controlled regions was unbounded (CVE-2022-42333), -     installation and removal of such regions was not properly serialized (CVE-2022-42334). (CVE-2022-42333,     CVE-2022-42334)

  - x86 shadow paging arbitrary pointer dereference In environments where host assisted address translation is     necessary but Hardware Assisted Paging (HAP) is unavailable, Xen will run guests in so called shadow mode.
    Due to too lax a check in one of the hypervisor routines used for shadow page handling it is possible for     a guest with a PCI device passed through to cause the hypervisor to access an arbitrary pointer partially     under guest control. (CVE-2022-42335)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 / openSUSE 15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2023:2535-1 advisory.

  - x86 shadow paging arbitrary pointer dereference In environments where host assisted address translation is     necessary but Hardware Assisted Paging (HAP) is unavailable, Xen will run guests in so called shadow mode.
    Due to too lax a check in one of the hypervisor routines used for shadow page handling it is possible for     a guest with a PCI device passed through to cause the hypervisor to access an arbitrary pointer partially     under guest control. (CVE-2022-42335)

  - Mishandling of guest SSBD selection on AMD hardware The current logic to set SSBD on AMD Family 17h and     Hygon Family 18h processors requires that the setting of SSBD is coordinated at a core level, as the     setting is shared between threads. Logic was introduced to keep track of how many threads require SSBD     active in order to coordinate it, such logic relies on using a per-core counter of threads that have SSBD     active. When running on the mentioned hardware, it's possible for a guest to under or overflow the thread     counter, because each write to VIRT_SPEC_CTRL.SSBD by the guest gets propagated to the helper that does     the per-core active accounting. Underflowing the counter causes the value to get saturated, and thus     attempts for guests running on the same core to set SSBD won't have effect because the hypervisor assumes     it's already active. (CVE-2022-42336)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 38 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2023-d28433ead1 advisory.

    x86 shadow paging arbitrary pointer dereference [XSA-430, CVE-2022-42335]

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
189976	GLSA-202402-07 : Xen: Multiple Vulnerabilities	Nessus	Gentoo Local Security Checks	high
177438	SUSE SLED15 / SLES15 / openSUSE 15 Security Update : xen (SUSE-SU-2023:2535-1)	Nessus	SuSE Local Security Checks	high
174914	Fedora 38 : xen (2023-d28433ead1)	Nessus	Fedora Local Security Checks	high

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CVE-2022-42335

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