---
id: CVE-2026-110240
title: >-
  Lancet through 2.3.9 contains an SSRF protection bypass vulnerability in
  netutil.IsInternalIP that misclassifies IPv6 private, link-local, CGNAT and
  transition addresses as external
summary: >-
  Lancet through 2.3.9 contains an SSRF protection bypass vulnerability in
  netutil.IsInternalIP that misclassifies IPv6 private, link-local, CGNAT and
  transition addresses as external. Attackers can supply hostnames resolving to
  these addr…
severity: medium
cvss: 4.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-918
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T20:17:28.220'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-110240'
references:
  - url: 'https://github.com/duke-git/lancet'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/duke-git/lancet/blob/v1.4.6/netutil/net.go#L158-L170'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/duke-git/lancet/blob/v2.3.9/netutil/net.go#L192-L205'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/duke-git/lancet/commit/835111c832939a85416d686a1e99d5fe7060c9b4
    label: disclosure@vulncheck.com
  - url: 'https://github.com/duke-git/lancet/issues/356'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/duke-git/lancet/pull/357'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/lancet-through-2.3.9-ssrf-protection-bypass-via-netutil-isinternalip
    label: disclosure@vulncheck.com
  - url: 'https://github.com/duke-git/lancet/issues/356'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
ingestedAt: '2026-10-13T19:43:28.944Z'
vendor: duke-git
product: lancet
affected:
  - lancet >= 2.1.2 <= 2.3.9
  - lancet >= 1.3.1 <= 1.4.6
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-13T19:24:08.615533Z'
---

## Overview

Lancet through 2.3.9 contains an SSRF protection bypass vulnerability in netutil.IsInternalIP that misclassifies IPv6 private, link-local, CGNAT and transition addresses as external. Attackers can supply hostnames resolving to these address forms, including NAT64, 6to4 or Teredo embedding internal IPv4, to reach internal services or cloud metadata endpoints.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.