CISA says attackers are exploiting SolarWinds Serv-U denial-of-service flaw CVE-2026-28318

CISA says hackers are now actively exploiting a recently patched SolarWinds Serv-U bug to crash exposed file-transfer servers. The flaw, CVE-2026-28318, affects SolarWinds Serv-U MFT and FTP software on Windows and Linux and can be triggered without authentication using specially crafted POST requests with Content-Encoding: deflate; SolarWinds fixed it in Serv-U 15.5.4 Hotfix 1 and advised admins who cannot patch to restrict access and block such requests.
Why it matters: Organizations running internet-exposed Serv-U servers could face service outages right now, including federal agencies ordered to remediate by June 19. If you use Serv-U, patch immediately or apply SolarWinds' temporary filtering and access restrictions while checking for signs of attempted abuse.

Sources

SolarWinds Serv-U Vulnerability Exploited in the Wild
Ionut Arghire 2026.06.08 98% relevant
This is the same underlying event: active exploitation of SolarWinds Serv-U CVE-2026-28318. The article adds patch timing details, notes the fix is Serv-U 15.5.4 Hotfix 1, explains the unauthenticated specially crafted POST request with the 'Content-Encoding: deflate' header, and reiterates affected/EoL versions and CISA's June 19 federal patch deadline.
CISA Adds Actively Exploited SolarWinds Serv-U DoS Flaw to KEV Catalog
info@thehackernews.com (The Hacker News) 2026.06.06 99% relevant
It covers the same underlying event: CISA adding the actively exploited SolarWinds Serv-U flaw CVE-2026-28318 to the Known Exploited Vulnerabilities catalog, reinforcing the exploitation status and remediation urgency for affected organizations.
CISA: Hackers now exploit SolarWinds Serv-U flaw to crash servers
Sergiu Gatlan 2026.06.05 100% relevant
This article establishes a new tracked story because it is the first item here tying SolarWinds Serv-U CVE-2026-28318 to active exploitation and CISA KEV inclusion.
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