Is CVE-2026-103503 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-103503 being exploited in the wild.

How severe is CVE-2026-103503?

Informational severity, published 12 October 2026.

Which products and versions are affected?

Hexpm Hex from 0.20.2 before 2.5.2.

Is there a fix for CVE-2026-103503?

Yes: fixed in 2.5.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-103503 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-103503?

Check whether you run Hexpm Hex at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-103503: hexpm hex improper certificate validation in SSL opts

CVE-2026-103503 · Severity: info · Published 2026-10-12

Hex is a package manager for Elixir that downloads dependencies over HTTPS. A flaw in certificate validation allows an attacker on the network to impersonate Hex repositories and intercept API keys and OAuth tokens if the user has configured a custom CA certificate store. The vulnerability bypasses the user's intended certificate restrictions by trusting Hex's bundled CA list regardless of the custom configuration.

Technologies: Hexpm Hex. Vendors: Hexpm.

Quick answers

Is CVE-2026-103503 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-103503 being exploited in the wild.
How severe is CVE-2026-103503?: Informational severity, published 12 October 2026.
Which products and versions are affected?: Hexpm Hex from 0.20.2 before 2.5.2.
Is there a fix for CVE-2026-103503?: Yes: fixed in 2.5.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-103503 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-103503?: Check whether you run Hexpm Hex at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: 2.5.2

Technical details

The vulnerability exists in Hex.HTTP.SSL where the partial_chain callback is built from the bundled CA store even when cacerts_path is configured to use a different CA store. This allows a certificate chain to be validated if any certificate in it matches a public key in the bundled store, bypassing the user's custom CA restrictions. An attacker holding a certificate for a Hex host issued by any CA in Hex's bundled store can impersonate that host to users who set cacerts_path to exclude that CA. Hostname verification still applies, so the attacker must hold a valid certificate for the target host.

Affected products

hexpm hex from 0.20.2 before 2.5.2

Timeline

2026-10-12: disclosed

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.