CISA: Patch actively exploited SolarWinds Serv-U DoS vulnerability (CVE-2026-28318)

CISA warned that CVE-2026-28318, an unauthenticated resource-consumption vulnerability in SolarWinds Serv-U triggered by POST requests with Content-Encoding: deflate, is being exploited in the wild; SolarWinds released Serv-U 15.5.4 Hotfix 1 to address it and CISA ordered federal agencies to remediate by June 19, 2026. Organizations are advised to apply the hotfix or mitigate via web application firewalls and access restrictions because the flaw can crash Serv-U servers and cause denial-of-service, potentially disrupting operations in regulated sectors.