Medium · CVSS 5.9CVE-2026-103503

Hex trusts its bundled CA certificates when cacerts_path is setCVE-2026-103503

Answer in brief

CVE-2026-103503 records a Medium severity (CVSS 5.9) vulnerability in Hex trusts its bundled CA certificates when cacerts_path is set. The current sources do not mark it as known exploited. The current feed maps hexpm/hex (generic), hexpm/hexpm/hex (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 12, 2026Updated Oct 12, 2026Source checked Oct 12, 2026First seen by HOL Oct 12, 2026Material review Oct 12, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.9
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 5.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps hexpm/hex (generic), hexpm/hexpm/hex (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
hexpm/hexgeneric	>=0.20.2 <2.5.2	2.5.2
hexpm/hexpm/hexgeneric	>=c9b26a46928bfcd546773571e09c1d05f4cd9fb7 <*	*

Recommended response

Check inventory. Check lockfiles and deployed manifests for hexpm/hex, hexpm/hexpm/hex.
Review the reported fix. Source-reported solution: Upgrade Hex to 2.5.2 or later, for example with mix local.hex. With cacerts_path (HEX_CACERTS_PATH) set, Hex then only accepts server certificates that chain to a CA in that file, and it doesn't trust copies of CA certificates sent by the server.

Evidence timeline and material changes

Published upstream
Oct 12, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 12, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 12, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.