libhttp/url.c in shellinabox through 2.20 has an implementation flaw in the HTTP request parsing logic. By sending a crafted multipart/form-data HTTP request, an attacker could exploit this to force shellinaboxd into an infinite loop, exhausting available CPU resources and taking the service down.

The HTTPS fallback implementation in Shell In A Box (aka shellinabox) before 2.19 makes it easier for remote attackers to conduct DNS rebinding attacks via the "/plain" URL.