CVE-2026-87886, Acronis Backup plugin for cPanel/WHM and extension for Plesk: local privilege escalation via insecure default permissions, CISA KEV-listed (CVSS 7.8)

CVE-2026-87886 (CVSS 7.8) is a local privilege-escalation flaw from incorrect default file permissions (CWE-276) in the Acronis Backup plugin for cPanel & WHM and extension for Plesk, both on Linux (Help Net Security, 2026-09-16). A local attacker who already holds low-privilege access on an affected hosting-panel server can escalate to elevated privileges by abusing the plugin's own file permissions; no remote or unauthenticated path is described. CISA added the flaw to its Known Exploited Vulnerabilities catalog on 2026-09-16 with a three-day remediation deadline, and Acronis's advisory, quoted by both Help Net Security and BleepingComputer, states exploitation has been detected "in the wild in limited, targeted attacks against Acronis Backup plugin for cPanel & WHM deployments" (BleepingComputer, 2026-09-15); Acronis itself told BleepingComputer that assessment rests on a single report from a "potentially affected" customer, not a broadly observed campaign, and has published no indicators. Help Net Security states there are currently no signs of active exploitation on Plesk deployments specifically, so the confirmed activity is limited to the cPanel & WHM plugin (Help Net Security, 2026-09-16). Fixed builds: cPanel & WHM plugin 1.9.3 HF3 (build 1.9.3.1021), Plesk extension build 1.8.11.638.