Xen Hypervisor EUVD-2026-98831

Requires the attacker to already control a guest domain on a Xen host that holds a read-only grant mapping shared from another domain via the grant table interface; the attacker then invokes GNTTABOP_cache_flush using invalidate-without-clean against that read-only mapping. Exploitation is limited to multi-domain/multi-tenant Xen deployments that use inter-domain memory sharing, and needs code execution inside a guest rather than any network access. Authentication requirements are not cleanly confirmed because the supplied CVSS vector (PR:N) appears to belong to the sibling CVE; in practice a running, attacker-controlled guest domain is the prerequisite.

Signals point to a moderate, situational priority rather than a top-tier emergency. The input CVSS base score of 7.5 and its vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) do NOT match this specific CVE: that vector describes an availability/denial-of-service impact and, together with the CWE-191 (integer underflow) and 'Denial Of Service'/'Integer Overflow' tags, clearly corresponds to the sibling issue CVE-2026-102699 in the same shared Xen record. CVE-2026-102702 is instead a memory-INTEGRITY flaw: a guest can issue GNTTABOP_cache_flush with invalidate-without-clean against a read-only grant mapping and corrupt another domain's memory - an integrity (I) impact, not the availability (A:H) shown. Exploitation probability is low (EPSS 0.15%, 3rd percentile), there is no CISA KEV listing and no public exploit identified, so this is not evidence of active or widespread exploitation. Realistically the attacker must already control a guest VM on a shared Xen host and hold a read-only inter-domain grant mapping, which confines risk to multi-tenant virtualization environments. Net: a credible cross-domain memory-corruption bug worth patching on shared hypervisors, but the provided CVSS vector should be treated as mislabeled and verified against Xen advisory XSA-519 before being used for prioritization.

A tenant who controls a guest domain on a shared Xen host maps memory that another domain granted to it read-only, then issues a GNTTABOP_cache_flush invalidate-without-clean operation against that mapping, corrupting the granting domain's memory contents. No public exploit code has been identified. Because the attacker must execute hypercalls from inside a guest, exploitation is local to the host rather than network-remote despite the input vector's AV:N.