libslirp vulnerabilities

A flaw was found in libslirp where, when handling ICMP echo requests, the reply length is not updated to match the actual data received from the host. Under specific conditions where the normal ICMP socket is unavailable, this length mismatch causes the host's real IP address to be leaked to the guest in the echo reply, breaking the NAT isolation that user-mode networking is expected to provide.

An out-of-bounds read was found in the NC-SI OEM response handler of libslirp. A truncated NC-SI OEM Ethernet frame causes ncsi_rsp_handler_oem() to read up to 4 bytes beyond the supplied packet length and reflect the value into the response sent to the guest, resulting in guest-observable disclosure.

A heap-based buffer overflow was found in the DHCPv6 and TFTP response builders of libslirp. When the host is configured with a small interface MTU, a guest-supplied DHCPv6 CLIENTID option or TFTP blksize option can overflow the reply buffer with attacker-controlled content and length, resulting in denial of service and potentially arbitrary code execution in the host process. The default interface MTU is not affected.