87 matches found
FreeBSD : xen-kernel -- broken check in memory_exchange() permits PV guest breakout (90becf7c-1acf-11e7-970f-002590263bf5)
The Xen Project reports : The XSA-29 fix introduced an insufficient check on XENMEMexchange input, allowing the caller to drive hypervisor memory accesses outside of the guest provided input/output arrays. A malicious or buggy 64-bit PV guest may be able to access all of system memory, allowing f...
FreeBSD : xen-kernel -- x86 PV guests may be able to mask interrupts (3ae078ca-c7eb-11e6-ae1b-002590263bf5)
The Xen Project reports : Certain PV guest kernel operations page table writes in particular need emulation, and use Xen's general x86 instruction emulator. This allows a malicious guest kernel which asynchronously modifies its instruction stream to effect the clearing of EFLAGS.IF from the state...
FreeBSD : xen-kernel -- x86: Mishandling of SYSCALL singlestep during emulation (942433db-c661-11e6-ae1b-002590263bf5)
The Xen Project reports : The typical behaviour of singlestepping exceptions is determined at the start of the instruction, with a DB trap being raised at the end of the instruction. SYSCALL and SYSRET, although we don't implement it behave differently because the typical behaviour allows userspa...
FreeBSD : xen-kernel -- x86 CMPXCHG8B emulation fails to ignore operand size override (80a897a2-c1a6-11e6-ae1b-002590263bf5)
The Xen Project reports : The x86 instruction CMPXCHG8B is supposed to ignore legacy operand size overrides; it only honors the REX.W override making it CMPXCHG16B. So, the operand size is always 8 or 16. When support for CMPXCHG16B emulation was added to the instruction emulator, this restrictio...
FreeBSD : xen-kernel -- guest 32-bit ELF symbol table load leaking host data (5555120d-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : Along with their main kernel binary, unprivileged guests may arrange to have their Xen environment load kernel symbol tables for their use. The ELF image metadata created for this purpose has a few unused bytes when the symbol table binary is in 32-bit ELF format. These...
FreeBSD : xen-kernel -- x86: Mishandling of instruction pointer truncation during emulation (49211361-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : When emulating HVM instructions, Xen uses a small i-cache for fetches from guest memory. The code that handles cache misses does not check if the address from which it fetched lies within the cache before blindly writing to it. As such it is possible for the guest to...
FreeBSD : xen-kernel -- use after free in FIFO event channel code (4bf57137-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : When the EVTCHNOPinitcontrol operation is called with a bad guest frame number, it takes an error path which frees a control structure without also clearing the corresponding pointer. Certain subsequent operations EVTCHNOPexpandarray or another EVTCHNOPinitcontrol, upon...
FreeBSD : xen-kernel -- x86: Disallow L3 recursive pagetable for 32-bit PV guests (45ca25b5-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : On real hardware, a 32-bit PAE guest must leave the USER and RW bit clear in L3 pagetable entries, but the pagetable walk behaves as if they were set. The L3 entries are cached in processor registers, and don't actually form part of the pagewalk. When running a 32-bit PV...
FreeBSD : xen-kernel -- x86 segment base write emulation lacking canonical address checks (53dbd096-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : Both writes to the FS and GS register base MSRs as well as the WRFSBASE and WRGSBASE instructions require their input values to be canonical, or a GP fault will be raised. When the use of those instructions by the hypervisor was enabled, the previous guard against GP...
FreeBSD : xen-kernel -- x86 task switch to VM86 mode mis-handled (523bb0b7-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : LDTR, just like TR, is purely a protected mode facility. Hence even when switching to a VM86 mode task, LDTR loading needs to follow protected mode semantics. This was violated by the code. On SVM AMD hardware: a malicious unprivileged guest process can escalate its...
FreeBSD : xen-kernel -- x86 64-bit bit test instruction emulation broken (56f0f11e-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : The x86 instructions BT, BTC, BTR, and BTS, when used with a destination memory operand and a source register rather than an immediate operand, access a memory location offset from that specified by the memory operand as specified by the high bits of the register source....
FreeBSD : xen-kernel -- x86 HVM: Overflow of sh_ctxt->seg_reg[] (4aae54be-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : x86 HVM guests running with shadow paging use a subset of the x86 emulator to handle the guest writing to its own pagetables. There are situations a guest can provoke which result in exceeding the space allocated for internal state. A malicious HVM guest administrator ca...
FreeBSD : xen-kernel -- CR0.TS and CR0.EM not always honored for x86 HVM guests (4d7cf654-ba4d-11e6-ae1b-002590263bf5)
The Xen Project reports : Instructions touching FPU, MMX, or XMM registers are required to raise a Device Not Available Exception NM when either CR0.EM or CR0.TS are set. Their AVX or AVX-512 extensions would consider only CR0.TS. While during normal operation this is ensured by the hardware, if ...
xen-kernel -- x86 task switch to VM86 mode mis-handled
The Xen Project reports: LDTR, just like TR, is purely a protected mode facility. Hence even when switching to a VM86 mode task, LDTR loading needs to follow protected mode semantics. This was violated by the code. On SVM AMD hardware: a malicious unprivileged guest process can escalate its...
FreeBSD : xen-kernel -- x86: Missing SMAP whitelisting in 32-bit exception / event delivery (04cf89e3-5854-11e6-b334-002590263bf5)
The Xen Project reports : Supervisor Mode Access Prevention is a hardware feature designed to make an Operating System more robust, by raising a pagefault rather than accidentally following a pointer into userspace. However, legitimate accesses into userspace require whitelisting, and the excepti...
FreeBSD : xen-kernel -- x86: Privilege escalation in PV guests (032aa524-5854-11e6-b334-002590263bf5) (Bunker Buster)
The Xen Project reports : The PV pagetable code has fast-paths for making updates to pre-existing pagetable entries, to skip expensive re-validation in safe cases e.g. clearing only Access/Dirty bits. The bits considered safe were too broad, and not actually safe. A malicious PV guest administrat...
xen-kernel -- x86: Missing SMAP whitelisting in 32-bit exception / event delivery
The Xen Project reports: Supervisor Mode Access Prevention is a hardware feature designed to make an Operating System more robust, by raising a pagefault rather than accidentally following a pointer into userspace. However, legitimate accesses into userspace require whitelisting, and the exceptio...
Vulnerabilities in the Debian GNU/Linux operating system that allow a remote attacker to compromise the confidentiality, integrity, and accessibility of protected information
The Linux-modules-2.6.26-1-xen-686 package from the Debian GNU/Linux operating system has multiple vulnerabilities. Exploitation of these vulnerabilities may lead to breaches of confidentiality, integrity, and accessibility of protected information. These vulnerabilities can be exploited remotely...
Vulnerabilities of the Debian GNU/Linux operating system that allow a remote attacker to compromise the accessibility of protected information
The Linux-modules-2.6.26-2-xen-686 package from the Debian GNU/Linux operating system has multiple vulnerabilities. Exploitation of these vulnerabilities may result in a violation of the accessibility of protected information. These vulnerabilities can be exploited remotely...
Vulnerabilities of the Debian GNU/Linux operating system that allow a remote attacker to compromise the accessibility of protected information
The Linux-image-2.6.26-2-xen-686 package from the Debian GNU/Linux operating system has multiple vulnerabilities. Exploitation of these vulnerabilities may lead to a violation of the accessibility of protected information. These vulnerabilities can be exploited remotely...