Docker, a one-time highflier in business software that reached a $1 billion valuation in 2015, is struggling mightily these days as it tries to raise some much-needed capital.

Rob Bearden, who was named CEO in May, wrote an email to employees this week thanking them for "persevering in spite of the lack of clarity we've had these past few weeks." In the note, which was viewed by CNBC, he told his staff that more cash is hopefully on the way.

"As shared at the last All Hands, we have been engaging with investors to secure more financing to continue to execute on our strategy," wrote Bearden, who was previously CEO of Hortonworks before the company merged with rival Cloudera last year. "I wanted to share a quick update on where we stand. We are currently in active negotiations with two investors and are working through final terms. We should be able to provide you a more complete update within the next couple of weeks."

A Docker spokesperson declined to comment.

While Docker may be able to secure additional capital, it's yet another company that finds itself in an ominous position after raising mounds of cash during the heady days earlier this decade. When Bearden joined in May, he became the fourth CEO and the third since 2017, replacing Steve Singh, a former senior executive at SAP. Docker's founder Solomon Hykes left the company last year, and Mariana Tessel, the executive vice president of strategic development, departed in 2017 for Intuit.

Docker popularized the use of technology called containers to package up source code so that developers could easily move their applications around from laptops to servers and to the cloud. Administrators use containers on servers as an alternative to the virtual machine technology that helped VMware become a dominant force in the data center.

Despite its widespread use, Docker's core software is open source, so anybody can download it for free and tinker with it. The company sells products to help businesses manage their deployments, but revenue hasn't taken off in a way that mirrors high-value subscription software players.