SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability
Serv-U 15.5.4 and below is affected by an unauthenticated crash from crafted POST requests using Content-Encoding: deflate. The fix is Serv-U 15.5.4 HF1.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Actively exploited
- Fix
- Fixed in SolarWinds Serv-U 15.5.4 HF1
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: active
- Automatable: yes
- Technical impact: partial
Summary
SolarWinds Serv-U is affected by a flaw that lets an unauthenticated attacker crash the service by sending specially crafted POST requests using Content-Encoding: deflate, causing a denial of service. Mitigation steps are available in the SolarWinds Trust Center for customers who cannot immediately deploy the update.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
SolarWinds Serv-U is susceptible to specially crafted POST requests that crash the Serv-U service without authentication using Content-Encoding: deflate. Mitigation steps are provided to secure customer environments in the SolarWinds Trust Center if you are unable to deploy the update
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: active · Automatable: yes · Technical impact: partial
- Added to CISA KEV
CISA has evidence of exploitation in the wild
- CISA remediation deadline
Due date for US federal agencies to patch
- Record last updated
- EPSS reached 10%
FIRST estimates at least a 10% chance of exploitation in the next 30 days
Affected versions
- SolarWinds Serv-U
through 15.5.4
References 2
solarwinds.com
documentation.solarwinds.com
Questions about CVE-2026-28318
What does this mean?
Specially crafted POST requests that use Content-Encoding: deflate can crash the Serv-U service without authentication, causing a denial of service.Source: solarwinds.com
Am I affected, and how do I check?
Serv-U version 15.5.4 and below is affected, and the issue involves POST requests that use Content-Encoding: deflate. Compare your installed Serv-U version with 15.5.4 to check whether the version range applies.Source: solarwinds.com
What should I do about it?
Upgrade to SolarWinds Serv-U 15.5.4 HF1. Until you can upgrade, block POST requests containing content-encoding at the web access firewall and limit access to known addresses where possible.Source: solarwinds.com
Is it being exploited?
Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-06-05, which means it has evidence of attacks. No public exploit code is tracked.Source: cisa.gov, cve.now feed data