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PatchSiren cyber security CVE debrief

CVE-2016-9382 Xen CVE debrief

CVE-2016-9382 describes a Xen flaw in x86 task switching to VM86 mode. According to NVD, the issue affects Xen 4.0.x through 4.7.x and selected Citrix XenServer releases. A local user inside a 32-bit x86 HVM guest may be able to gain privileges or crash the guest OS, depending on how the guest operating system uses hardware task switching and starts new tasks in VM86 mode. NVD rates the issue HIGH with CVSS 3.0 vector CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Vendor
Xen
Product
CVE-2016-9382
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2017-01-23
Original CVE updated
2026-05-13
Advisory published
2017-01-23
Advisory updated
2026-05-13

Who should care

Xen and XenServer administrators, virtualization platform owners, and teams responsible for guest OS hardening should care most. The exposure is relevant where older Xen-based hosts run 32-bit x86 HVM guests that use hardware task switching.

Technical summary

NVD states that Xen mishandles x86 task switches into VM86 mode. The vulnerable configurations listed in the CPE criteria span Xen 4.0.0 through 4.7.1 and Citrix XenServer 6.0.2, 6.2.0, 6.5, and 7.0. The issue is local to the guest context and requires low privileges in the guest. The primary impact described by NVD is privilege escalation within the guest or a guest OS crash. NVD also maps the weakness to CWE-264.

Defensive priority

High for environments that still run affected Xen or XenServer versions, especially with legacy 32-bit x86 HVM guests. The combination of local attack conditions and potential confidentiality, integrity, and availability impact justifies prompt patching.

Recommended defensive actions

  • Review whether any hosts run the Xen or Citrix XenServer versions listed by NVD as vulnerable.
  • Apply the vendor and distribution fixes referenced by Xen advisory XSA-192 and related vendor notices.
  • Prioritize upgrades or maintenance windows for systems hosting legacy 32-bit x86 HVM guests that rely on hardware task switching.
  • Validate guest and host inventories against the affected CPE versions before and after remediation.
  • Monitor vendor advisories and package updates for the specific Xen/XenServer branches in use.

Evidence notes

All substantive claims in this debrief come from the supplied NVD record and its referenced vendor/advisory links. The NVD description states the VM86 task-switch issue, the affected Xen and Citrix XenServer versions, and the guest-local privilege escalation or DoS outcome. NVD also provides the CVSS 3.0 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H and CWE-264 classification. Timing context uses the CVE publishedAt value of 2017-01-23T21:59:02.830Z and modifiedAt value of 2026-05-13T00:24:29.033Z; no other dates are used as the issue date.

Official resources

CVE-2016-9382 was published in the CVE/NVD record on 2017-01-23T21:59:02.830Z and later modified on 2026-05-13T00:24:29.033Z. The source corpus does not provide a separate vendor disclosure timestamp, so those CVE record dates are the only