---
title: "Security Bulletin: SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability"
description: CVE-2026-28318 is a SolarWinds Serv-U DoS vulnerability with KEV listing. Patch immediately to prevent service disruption and outages.
---

[Cybersecurity Blog | RedLegg ](https://www.redlegg.com/blog)

# [Security Bulletin: SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability](https://www.redlegg.com/blog/security-bulletin-solarwinds-serv-u-dos)

 Written by [RedLegg's Cyber Threat Intelligence Team](https://www.redlegg.com/blog/author/redleggs-cyber-threat-intelligence-team) | 6/5/26 9:21 PM

About:

CVE-2026-28318 is a high-severity unauthenticated denial of service vulnerability in SolarWinds Serv-U that is listed in CISA’s KEV catalog. Attackers can exploit the flaw to disrupt file transfer services and make systems unavailable. Organizations should urgently apply the 15.5.4 Hotfix 1 update and prioritize internet-facing deployments.

RedLegg will occasionally communicate vulnerabilities released outside the usual release schedule to provide additional value to our customers. These emergency bulletins describe vulnerabilities or threats we classify as the highest severity level and warrant out-of-band emergency patching or mitigation action.

## VULNERABILITIES

## SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability

 

Identifier: CVE-2026-28318   
PoC or Exploitation:   
CVE-2026-28318 has been added to the CISA Known Exploited Vulnerabilities (KEV) Catalog.   
**CVSS Score: ****7.5 (High, CVSS v3.1)**

Update / Patch:  
SolarWinds has released a security update addressing this vulnerability.

Affected versions include:   
SolarWinds Serv-U 15.5.4 and below

Fixed version:   
SolarWinds Serv-U 15.5.4 Hotfix 1

Vendor advisory and patch guidance:   
**[https://www.solarwinds.com/trust-center/security-advisories/CVE-2026-28318](https://www.solarwinds.com/trust-center/security-advisories/CVE-2026-28318?utm_campaign=Threat%20Intel&utm_source=hs_email&utm_medium=email&_hsenc=p2ANqtz--GThbJCIG_F00y5rbTfui4XSVQIFRa5sL2KxaFMg8ptiQhpWsl8FOzpVL9w1JMXel-D0QT)**

Release notes:   
**[https://documentation.solarwinds.com/en/success_center/servu/content/release_notes/servu_15-5-4-hotfix-1_release_notes.htm](https://documentation.solarwinds.com/en/success_center/servu/content/release_notes/servu_15-5-4-hotfix-1_release_notes.htm?utm_campaign=Threat%20Intel&utm_source=hs_email&utm_medium=email&_hsenc=p2ANqtz--GThbJCIG_F00y5rbTfui4XSVQIFRa5sL2KxaFMg8ptiQhpWsl8FOzpVL9w1JMXel-D0QT)**

**Description:   
**CVE-2026-28318 is an unauthenticated denial of service vulnerability affecting SolarWinds Serv-U.

Successful exploitation can cause the Serv-U service to become unavailable, resulting in denial of service conditions and disruption of file transfer operations.

**Mitigation Recommendation:   
**Immediately upgrade affected SolarWinds Serv-U installations to version 15.5.4 Hotfix 1.

Identify internet-facing Serv-U deployments and prioritize them for remediation.

Review application and system logs for unexpected service interruptions, crashes, resource exhaustion events, or anomalous connection activity.

Implement network access controls to limit exposure of Serv-U services where operationally feasible.

Monitor affected systems for recurring denial of service conditions and investigate any unexplained availability issues.

Verify that backup and recovery procedures are in place to support rapid restoration of affected services if disruption occurs.

 

[View full post](https://www.redlegg.com/blog/security-bulletin-solarwinds-serv-u-dos)

```json
{
  "@context" : "http://schema.org",
  "@type" : "BlogPosting",
  "author" : {
    "@type" : "Person",
    "name" : "RedLegg's Cyber Threat Intelligence Team"
  },
  "dateModified" : "2026-06-05T21:21:43.274Z",
  "datePublished" : "2026-06-05T21:21:43Z",
  "headline" : "Emergency Security Bulletin: SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability",
  "image" : {
    "@type" : "ImageObject",
    "height" : 630,
    "url" : "https://www.redlegg.com/hubfs/Emergency%20Bulletin%20v2.png",
    "width" : 1200
  },
  "mainEntityOfPage" : "https://www.redlegg.com/blog/security-bulletin-solarwinds-serv-u-dos",
  "publisher" : {
    "@type" : "Organization",
    "logo" : {
      "@type" : "ImageObject",
      "height" : 60.0,
      "url" : "https://cdn2.hubspot.net/hubfs/4675768/logo-red-01.png",
      "width" : 419.66666
    },
    "name" : "RedLegg Cybersecurity Blog"
  }
}
```