{"cve":"CVE-2021-21788","nvd":{"published":"2021-07-07T17:15:07.987","modified":"2026-06-17T03:36:07.103","status":"Modified","description":"A privilege escalation vulnerability exists in the way IOBit Advanced SystemCare Ultimate 14.2.0.220 driver handles Privileged I/O write requests. During IOCTL 0x9c40a0dc, the first dword passed in the input buffer is the device port to write to and the word at offset 4 is the value to write via the OUT instruction. The OUT instruction can write one byte to the given I/O device port, potentially leading to escalated privileges of unprivileged users. A local attacker can send a malicious IRP to trigger this vulnerability.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","score":8.8},"cwes":["CWE-782"],"references":["https://talosintelligence.com/vulnerability_reports/TALOS-2021-1254","https://talosintelligence.com/vulnerability_reports/TALOS-2021-1254"],"products":["iobit:advanced_systemcare_ultimate"],"source":"nvd","synced_at":"2026-10-19T21:20:07.141963181+00:00"},"epss":{"cve":"CVE-2021-21788","score":0.00321,"percentile":0.25179,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}