---
id: CVE-2026-103503
title: >-
  Improper Certificate Validation vulnerability in hexpm hex allows an attacker
  who can intercept HTTPS connections, and holds a certificate for a Hex host
  issued by a CA in Hex's bundled CA store, to impersonate that host to users
  who set…
summary: >-
  Improper Certificate Validation vulnerability in hexpm hex allows an attacker
  who can intercept HTTPS connections, and holds a certificate for a Hex host
  issued by a CA in Hex's bundled CA store, to impersonate that host to users
  who set…
severity: none
cwe:
  - CWE-295
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T16:17:02.427'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-103503'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-103503.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-103503'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
ingestedAt: '2026-10-12T16:57:59.908Z'
---

## Overview

Improper Certificate Validation vulnerability in hexpm hex allows an attacker who can intercept HTTPS connections, and holds a certificate for a Hex host issued by a CA in Hex's bundled CA store, to impersonate that host to users who set cacerts_path to a CA store that leaves that CA out.

cacerts_path (HEX_CACERTS_PATH) is documented as the path to the CA certificate store, used instead of the CA bundle that ships with Hex. Hex.HTTP.SSL.ssl_opts/1 passes the configured store as the cacerts option, but builds the partial_chain callback from the bundled store whether cacerts_path is set or not. Hex.HTTP.SSL.partial_chain/2 accepts a server chain when any certificate in it has the same public key as a bundled CA certificate, so a chain that leads to a bundled CA passes verification although the configured store doesn't contain that CA. Hostname verification still applies.

This issue affects hex: from 0.20.2 before 2.5.2.

## Remediation

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