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.

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.