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Fencer Vulns
high 7.8

CVE-2009-4031 json

The do_insn_fetch function in arch/x86/kvm/emulate.c in the x86 emulator in the KVM subsystem in the Linux kernel before 2.6.32-rc8-next-20…

published 2009-11-27 16 y ago modified 2026-06-16 4 mo ago also EUVD-2009-4002

cvss
7.8
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

The do_insn_fetch function in arch/x86/kvm/emulate.c in the x86 emulator in the KVM subsystem in the Linux kernel before 2.6.32-rc8-next-20091125 tries to interpret instructions that contain too many bytes to be valid, which allows guest OS users to cause a denial of service (increased scheduling latency) on the host OS via unspecified manipulations related to SMP support.

Patch / fix

  • linux linux_kernel 2.6.32
  • rhev-hypervisor RHEL 5 5.4-2.1.3.el5_4rhev2_1
  • rhev-hypervisor-pxe RHEL 5 5.4-2.1.3.el5_4rhev2_1
  • kvm RHEL 5 VIRTUALIZATION 83-105.el5_4.13
  • kmod-kvm RHEL 5 VIRTUALIZATION 83-105.el5_4.13
  • kvm-tools RHEL 5 VIRTUALIZATION 83-105.el5_4.13
  • kvm-qemu-img RHEL 5 VIRTUALIZATION 83-105.el5_4.13

red hat advisories RHSA-2009:1692RHSA-2009:1659

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2009-4031 updated cvss 2.1

kernel: KVM: x86 emulator: limit instructions to 15 bytes

  • Red Hat Enterprise Linux Desktop Multi OS (v. 5 client) kvm 83-105.el5_4.13, kmod-kvm 83-105.el5_4.13, kvm-tools 83-105.el5_4.13, kvm-qemu-img 83-105.el5_4.13 Red Hat Enterprise Linux Virtualization (v. 5 server) kvm 83-105.el5_4.13, kmod-kvm 83-105.el5_4.13, kvm-tools 83-105.el5_4.13, kvm-qemu-img 83-105.el5_4.13
    fixed: vendor fix RHSA-2009:1659
  • Red Hat Enterprise Virtualization Hypervisor 5 rhev-hypervisor 5.4-2.1.3.el5_4rhev2_1, rhev-hypervisor-pxe 5.4-2.1.3.el5_4rhev2_1
    fixed: vendor fix RHSA-2009:1692

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.11% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 2.0 7.8 AV:N/AC:L/Au:N/C:N/I:N/A:C

Classification

Weakness
  • CWE-20 Improper Input Validation
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.