CVE-2018-12891

NameCVE-2018-12891
DescriptionAn 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDLA-1577-1, DSA-4236-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
xen (PTS)buster, buster (security)4.11.4+107-gef32c7afa2-1fixed
bullseye4.14.6-1fixed
bullseye (security)4.14.5+94-ge49571868d-1fixed
bookworm4.17.3+10-g091466ba55-1~deb12u1fixed
trixie4.17.3+10-g091466ba55-1fixed
sid4.17.3+36-g54dacb5c02-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
xensourcejessie4.4.4lts4-0+deb8u1DLA-1577-1
xensourcestretch4.8.3+xsa267+shim4.10.1+xsa267-1+deb9u9DSA-4236-1
xensource(unstable)4.8.3+xsa267+shim4.10.1+xsa267-1+deb9u9

Notes

https://xenbits.xen.org/xsa/advisory-264.html

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