---
id: "CVE-2026-115449"
kind: "vulnerability"
aliases: ["CVE-2026-115449"]
title: "libslirp: ICMP echo reply leaks host IP to guest"
severity: "low"
cvss: 3.5
epss: 0.00226
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "libslirp", "qemu", "self-hosted", "virtualization"]
not_affected_if: ["bridged-or-tap-networking", "no-user-mode-networking"]
published_at: "2026-10-22T22:18:06+00:00"
first_seen_at: "2026-10-23T21:57:32+00:00"
updated_at: "2026-10-25T04:45:34+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115449", "first_seen_at": "2026-10-23T21:57:32+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-115449", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# libslirp: ICMP echo reply leaks host IP to guest

libslirp, the user-mode networking library used by QEMU and similar tools, mishandles ICMP echo replies when the normal ICMP socket is unavailable. A reply length mismatch leaks the host's real IP address to the guest, breaking NAT isolation.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-23T21:57:32+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115449
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-115449

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_