CVE-2026-115449
LowCVSS 3.5Summary
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.
Risk Assessment
Leaking the host's real IP address to a guest can bypass network isolation and aid further attacks or infrastructure reconnaissance. The risk affects environments using libslirp for user-mode network emulation.
Recommendation
Update libslirp to a version containing the fix or limit use of user-mode networking in higher-risk scenarios. Monitor ICMP traffic between guest and host for unusual replies.
Other vulnerabilities in libslirp
See all- CVE-2026-95507Medium
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.
- CVE-2026-95508High
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.
Original NVD description (English source)
A flaw was found in libslirp. 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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS