CVE-2026-102699
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Cache Flush Underflow in Xen Hypervisor

Publication date: 2026-10-13

Last updated on: 2026-10-13

Assigner: Xen Project

Description
[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] 1) XSA-437 (CVE-2023-34321) addressed issues with overflows in calculations involved in guests flushing caches through GNTTABOP_cache_flush. Unfortunately the fix there introduced a calculation which may underflow, resulting in a loop which would - at least on 64-bit Arm - take excessively long, and which would likely eventually crash the hypervisor. This is CVE-2026-102699. 2) GNTTABOP_cache_flush may be issued on memory mapped from another domain using the grant table interface. However there was no restriction to disallow the use of invalidate-without-clean against read-only grant mappings, which may corrupt the granted memory. This is CVE-2026-102702.

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Meta Information

Published
2026-10-13
Last Modified
2026-10-13
Generated
2026-10-19
AI Q&A
2026-10-13
EPSS Evaluated
2026-10-18
NVD
CVE-2026-102699
EUVD
EUVD-2026-98830

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
xen xen *
xen xen From 4.5 (inc)

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

CVE-2026-102699 is a vulnerability in Xen hypervisor versions 4.5 and later affecting 64-bit Arm systems. It involves a calculation underflow in cache flush operations that can cause an excessively long loop, potentially crashing the hypervisor. This flaw was introduced by a previous fix for another issue.

Detection Guidance

Detection requires checking Xen hypervisor versions and applying patches. Monitor system logs for hypervisor crashes or excessive CPU usage on Arm systems running Xen 4.5+. Use 'xl info' to check Xen version and 'dmesg' for crash logs.

Impact Analysis

An attacker could exploit this to crash the hypervisor, causing a Denial of Service. This may lead to system downtime or instability. In some cases, it could also enable privilege escalation or information leaks if combined with other vulnerabilities.

Compliance Impact

This vulnerability primarily impacts system availability and integrity by allowing denial of service or memory corruption in Xen hypervisors on Arm systems. It does not directly affect compliance with GDPR or HIPAA unless such incidents lead to data breaches or service disruptions that violate those regulations.

Mitigation Strategies

Apply available patches for Xen versions 4.5 and later. Update to the latest stable release. Restart the hypervisor after patching. Isolate untrusted guests until patched.

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