A flaw was found in SSSD. The sssnssprotocolparseaddr() function in the NSS responder (src/responder/nss/nssprotocol.c) extracts a 32-bit addrlen value from the client request but only validates that the body is at least 8 bytes, without checking that addrlen fits within the remaining packet body. This unvalidated length is passed through to tallocmemdup() in cachereqdatacreate(), which copies addrlen bytes from the small request buffer, causing a heap-buffer-overflow read. A local attacker can trigger this by connecting to the world-writable NSS responder socket (/var/lib/sss/pipes/nss) and sending a SSSNSSGETHOSTBYADDR (0x0053) request with a large addrlen value and a valid address family payload so that inetntop() succeeds. Successful exploitation crashes the sssdnss responder, causing a denial of service for NSS name resolution. Reported via PSIRTSUPT-20553 by BreachX Zero Day Labs.
A flaw was found in sssd. When authenticating with a YubiKey, the SSSD PAM responder can crash due to a use-after-free vulnerability, where a memory pointer is incorrectly handled. A local attacker could exploit this flaw by manipulating smartcard or YubiKey contents, leading to a denial of service that disrupts authentication. This vulnerability also presents a potential for privilege escalation, although it is difficult to exploit.
A flaw was found in the System Security Services Daemon (SSSD). The pampasskeychildreaddata() function within the PAM passkey responder fails to properly handle raw bytes received from a pipe. Because the data is treated as a NUL-terminated C string without explicit termination, it results in an out-of-bounds read when processed by functions like snprintf(). A local attacker could potentially trigger this vulnerability by initiating a crafted passkey authentication request, causing the SSSD PAM responder to crash, resulting in a local Denial of Service (DoS).
A memory leak was found in the sssdpacplugin (sssdpacplugin.so library), which is distributed with the sssdclient package.
Original report with additional details:
https://fedorahosted.org/sssd/ticket/2803
Patch:
https://fedorahosted.org/sssd/attachment/ticket/2803/0001-Fix-memory-leak-in-sssdpacverify.patch
Ted Brunell reported that SSSD, when authenticating against an LDAP server that allows unauthenticated binds, would authenticate users providing an empty password to any service using pamauthenticate (such as the GNOME screensaver). This could allow a local or remote attacker to gain access to an account without knowing the victim's password.
This flaw can only be exploited if the directory server allows unauthenticated binds, because the directory server will return that the bind was successful if no password is provided.
Acknowledgements:
Red Hat would like to thank Ted Brunell for reporting this issue.