libc in OpenBSD 6.6 allows authentication bypass via the -schallenge...

Vulnerability Description

libc in OpenBSD 6.6 allows authentication bypass via the -schallenge username, as demonstrated by smtpd, ldapd, or radiusd. This is related to gen/auth_subr.c and gen/authenticate.c in libc (and login/login.c and xenocara/app/xenodm/greeter/verify.c).

References

• https://www.openwall.com/lists/oss-security/2019/12/04/5
• https://www.openbsd.org/errata66.html
• http://www.openwall.com/lists/oss-security/2019/12/04/6
• http://www.openwall.com/lists/oss-security/2019/12/04/5
• https://seclists.org/bugtraq/2019/Dec/8
• http://packetstormsecurity.com/files/155572/Qualys-Security-Advisory-OpenBSD-Authentication-Bypass-Privilege-Escalation.html
• http://seclists.org/fulldisclosure/2019/Dec/14