SolarWinds Serv-U DoS via Malformed POST Request

Detection Guidance

This vulnerability involves specially crafted POST requests with the header Content-Encoding: deflate that cause the Serv-U service to crash without authentication.

To detect this vulnerability on your network or system, you can monitor for unusual crashes or service interruptions of the Serv-U service, especially following POST requests containing the Content-Encoding: deflate header.

You may also capture and analyze network traffic to identify POST requests with the Content-Encoding: deflate header targeting the Serv-U service.

• Use network packet capture tools like tcpdump or Wireshark to filter HTTP POST requests with Content-Encoding: deflate. For example, with tcpdump:
• tcpdump -i <interface> -A 'tcp port 80 or tcp port 443' | grep -i 'Content-Encoding: deflate'
• Check Serv-U service logs for crashes or restarts that correlate with such requests.

Note that no specific detection commands are provided in the available resources, but monitoring for these indicators can help identify exploitation attempts.

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Executive Summary

CVE-2026-28318 is a high-severity vulnerability in SolarWinds Serv-U that allows an attacker to crash the Serv-U service by sending specially crafted POST requests using the Content-Encoding: deflate header.

This attack can be performed without any authentication, meaning anyone who can send requests to the service can exploit this flaw.

The vulnerability causes a denial of service by crashing the service, disrupting its normal operation.

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Impact Analysis

This vulnerability can impact you by causing a denial of service on the SolarWinds Serv-U service.

An attacker can crash the service without authentication, leading to service downtime and potential disruption of business operations that rely on Serv-U.

Until the vulnerability is patched, affected environments remain at risk of being taken offline by such attacks.

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Mitigation Strategies

To mitigate the CVE-2026-28318 vulnerability in SolarWinds Serv-U, you should apply the hotfix provided in Serv-U version 15.5.4 Hotfix 1, which patches the affected components and prevents unauthenticated denial of service attacks.

• Stop the Serv-U processes before applying the hotfix.
• Back up key files to ensure you can restore the system if needed.
• Extract and apply the hotfix as per the instructions.
• Restart the Serv-U service after applying the hotfix.

If you are unable to deploy the update immediately, follow the mitigation steps provided in the SolarWinds Trust Center to secure your environment until the patch can be applied.

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Compliance Impact

The provided information does not specify any direct impact of CVE-2026-28318 on compliance with common standards and regulations such as GDPR or HIPAA.

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