Microsoft discovered a vulnerability in Serv-U that hackers exploited to carry out Log4j attacks on internal devices in the network of victim companies.
The bug was discovered by Microsoft experts while monitoring attacks using Log4j . The bug, identified as CVE-2021-35247 , was related to incorrect input validation, which allowed attackers to create requests and send them over the network in an unverified form.
SolarWinds, which is responsible for the development of Serv-U, has already published a security bulletin on CVE-2021-35247, and also released Serv-U version 15.3, which fixed the issue.
“The Serv-U web login for LDAP authentication allowed characters to be used that were not properly sanitized. SolarWinds has updated the input engine, adding an additional input validation and sanitization routine,” the developers write.
Interestingly, the company claims that the LDAP servers ignored invalid characters, that is, no further development of the attack allegedly could occur. Thus, it is not yet clear whether the attackers tried to exploit the vulnerability and failed, or whether the attacks successfully continued by exploiting problems in Log4j, as Microsoft stated.