A vulnerability was found in libssh, where the authentication check of the connecting client can be bypassed in thepkiverifydatasignature function in memory allocation problems. This issue may happen if there is insufficient memory or the memory usage is limited. The problem is caused by the return value rc, which is initialized to SSHERROR and later rewritten to save the return value of the function call pkikeycheckhashcompatible. The value of the variable is not changed between this point and the cryptographic verification. Therefore any error between them calls goto error returning SSHOK.