SolarWinds Serv-U Vulnerability Exploited in the Wild

Summary

CISA has issued a warning about active exploitation of a SolarWinds Serv-U vulnerability, tracked as CVE-2026-28318. This denial-of-service flaw, with a CVSS score of 7.5, can be exploited by unauthenticated attackers via specially crafted POST requests. SolarWinds has released a hotfix, and CISA is urging federal agencies to patch by June 19th, while advising all organizations to apply the update promptly.

Full text

The US cybersecurity agency CISA on Friday warned of attacks targeting a SolarWinds Serv-U vulnerability that had been patched a couple of days earlier. Tracked as CVE-2026-28318 (CVSS score of 7.5), the bug is described as a denial-of-service (DoS) issue that can be exploited via specially crafted POST requests to crash the Serv-U service. Successful exploitation of the security defect does not require authentication, SolarWinds warned on Thursday. The flaw was addressed in Serv-U 15.5.4 Hotfix 1. SolarWinds encourages all customers to download and install the hotfix, including those who recently upgraded to Serv-U 15.5.4. According to SolarWinds, the hotfix prevents attackers from crashing the Serv-U service via requests containing the ‘Content-Encoding: deflate’ header and some data. Users of Serv-U versions 15.4.2, 15.5, and 15.5.1, which have reached End-of-Life (EoL), are advised to upgrade to a supported release as soon as possible.Advertisement. Scroll to continue reading. While SolarWinds’s advisory makes no mention of CVE-2026-28318 being exploited in the wild, CISA on Friday added the bug to its Known Exploited Vulnerabilities (KEV) catalog. It’s unclear who is behind the attacks and whether the vulnerability has been exploited as a zero-day. In line with Binding Operational Directive (BOD) 22-01’s requirements, CISA urged federal agencies to patch the CVE by June 19 to keep their networks protected against active threats. While BOD 22-01 only applies to federal agencies, all organizations are advised to apply SolarWinds’ hotfix as soon as possible. The company’s advisory contains detailed instructions on installing the hotfix and on removing it if necessary. 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Indicators of Compromise

• cve — CVE-2026-28318

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