It was reported [1] that wpasupplicant does not properly check certificate subject name, which might lead to "man in the middle" attack. Relevant part of the original report: ...

wpasupplicant, linked against openssl performs this check:

if (depth == 0 && match && osstrstr(buf, match) == NULL) { wpaprintf(MSGWARNING, "TLS: Subject '%s' did not " "match with '%s'", buf, match); preverifyok = 0; openssltlsfailevent(conn, errcert, err, depth, buf, "Subject mismatch", TLSFAILSUBJECTMISMATCH); }

strstr() is vulnerable to extension attack, for instance, one would like to match on /CN=wireless.nikhef.nl, but explicitly not match on wireless.nikhef.nl.honestachmed.tr. There is no way to implement a secure EAP-TTLS/PEAP configuration using public certificates this way.

When linked against GnuTLS, the problem is even worse:

if (i == 0) { / TODO: validate subjectmatch and altsubjectmatch / }

Now, it is current best practice to run EAP-TTLS/PEAP with public certificates, because on Windows, this automatically pins the CN and CA from the certificate. ...

[1]: https://bugzilla.redhat.com/showbug.cgi?id=1178263