CVE-2018-12891
Status: ModifiedMedium (6.5)—
An 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.
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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.
CVSS
- Version: 3.0
- Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- Base score: 6.5
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.43%
- Percentile among all scored CVEs: 36
- Score date: 10/19/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (2)
CWEs
- NVD-CWE-noinfo
References
- http://www.openwall.com/lists/oss-security/2018/06/27/10
- http://www.securityfocus.com/bid/104570
- http://www.securitytracker.com/id/1041201
- http://xenbits.xen.org/xsa/advisory-264.html
- https://lists.debian.org/debian-lts-announce/2018/11/msg00013.html
- https://security.gentoo.org/glsa/201810-06
- https://support.citrix.com/article/CTX235748
- https://www.debian.org/security/2018/dsa-4236
- http://www.openwall.com/lists/oss-security/2018/06/27/10
- http://www.securityfocus.com/bid/104570
- http://www.securitytracker.com/id/1041201
- http://xenbits.xen.org/xsa/advisory-264.html
- https://lists.debian.org/debian-lts-announce/2018/11/msg00013.html
- https://security.gentoo.org/glsa/201810-06
- https://support.citrix.com/article/CTX235748
- https://www.debian.org/security/2018/dsa-4236
Raw JSON (NVD)
Show
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"value": "An 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."
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"value": "Se ha descubierto un problema en Xen hasta las versiones 4.10.x. Ciertas operaciones PV MMU podrían necesitar mucho tiempo para ser procesadas. Por este motivo, Xen comprueba explícitamente la necesidad de \"preempt\" la vCPU actual en ciertos momentos. Algunas rutas de código raramente tomadas omitieron estas comprobaciones. Forzando adecuadamente las condiciones mediante los contenidos de su propia tabla de página, un usuario malicioso podría hacer que estas omisiones sean empleadas para un número ilimitado de iteraciones. Un invitado PV malicioso o con errores podría provocar una denegación de servicio (DoS) que afecte al host entero. Específicamente, podría prevenir el uso de una CPU física durante un período de tiempo indeterminado. Todas las versiones de Xen desde la 3.4 en adelante son vulnerables. Las versiones de Xen 3.3 y anteriores son vulnerables a una clase de ataques incluso mayor, debido a que carecen de comprobaciones preemption en las rutas de código afectadas. Solo se han visto afectados los sistemas x86. Los sistemas ARM no se han visto afectados. Solo los invitados multi-vCPU x86 PV pueden aprovechar la vulnerabilidad. Ni los invitados x86 HVM ni los PVH, así como los x86 single-vCPU PV pueden aprovechar la vulnerabilidad."
}
],
"lastModified": "2026-06-17T01:38:31.213",
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