{"containers":{"cna":{"affected":[{"product":"XenServer","vendor":"Cloud Software Group","versions":[{"status":"affected","version":"all","versionType":"custom"}]},{"product":"XCP-ng","vendor":"Vates","versions":[{"status":"affected","version":"all","versionType":"custom"}]}],"credits":[{"lang":"en","type":"finder","value":"Jakob Wolffhechel, Moksha"}],"descriptions":[{"lang":"en","value":"A vm-admin in XAPI-based hypervisors (XenServer, XCP-ng) can downgrade a target VM's I/O scheduling class to idle by setting sched=idle in VBD.qos_algorithm_params. The idle class causes the kernel to service VBD kernel threads only when no other I/O is pending. Under any host I/O load, the target VM experiences severe I/O starvation. The field has zero map_keys_roles entries, and QoS changes take effect immediately via hot-apply without VBD replug."}],"metrics":[{"cvssV3_1":{"baseScore":5.3,"baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","version":"3.1"},"format":"CVSS"},{"cvssV4_0":{"baseScore":5.3,"baseSeverity":"MEDIUM","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","version":"4.0"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","description":"Missing Authorization","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-20","description":"Improper Input Validation","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-04-24T06:00:00Z","orgId":"moksha.dk","shortName":"Moksha"},"references":[{"url":"https://cna.moksha.dk/MOKSHA-2026-0061"}],"title":"I/O Scheduling Downgrade to Idle Class via VBD.qos_algorithm_params"}},"cveMetadata":{"alternateIds":["GCVE-117-2026-0061"],"assignerOrgId":"moksha.dk","cveId":"MOKSHA-2026-0061","datePublished":"2026-04-24T06:00:00Z","state":"PUBLISHED","x_moksha_note":"Self-issued advisory. MOKSHA-2026-NNNN is not a MITRE CVE ID. Schema follows CVE JSON 5.1 for tooling compatibility. alternateIds contains GCVE cross-references (GNA #117) and will also carry MITRE CVE IDs if assigned."},"dataType":"CVE_RECORD","dataVersion":"5.1","vulnerability-lookup:id":"moksha-2026-0061","vulnerability-lookup:score":1777010400.0}