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.