December 9, 2023

SolarWinds released patches for a Serv-U vulnerability that Microsoft says has been abused for the propagation of Log4j attacks.

A multi-protocol file server, SolarWinds Serv-U can be used for sending/receiving files to/from systems on the network. Administrators can create accounts for users and give them permissions to access specific files and folders stored on the server or another network resource.

Tracked as CVE-2021-35247, this input validation bug allows an attacker to build a query based on a given input and then send the query over the network, without sanitization, according to Microsoft, whose researchers discovered the flaw.


The Serv-U web login screen to LDAP authentication was allowing characters that were not sufficiently sanitized. SolarWinds resolved the security error by updating the input mechanism, so that it performs additional validation and sanitization.

This vulnerability was identified while monitoring threats exploiting the Log4j vulnerabilities when some attacks were observed being propagated via CVE-2021-35247.  Its recommended organizations that use Serv-U to apply the available security updates as soon as possible.

SolarWinds Serv-U 15.3 is the first version of the server to contain patches for the bug. Serv-U 15.2.5 and previous versions are vulnerable.

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