CVE-2026-103503 hexpm CVE debrief

Who should care

Defenders responsible for systems using the hex package should assess exposure based on their specific deployment contexts and verify their inventory of systems. They should evaluate the configuration of cacerts_path and its impact on the system's trust store. Additionally, they should consider updating to version 2.5.2 or later of the hex package. Defenders should prioritize verifying their inventory of systems using hex and assessing exposure based on их

Why it matters

The vulnerability in hexpm's hex package allows an attacker to impersonate a host to users who set cacerts_path to a CA store that leaves a specific CA out, impacting defenders who need to verify their inventory and assess exposure.

• Defenders need to verify their inventory of systems using hex and assess exposure based on specific deployment contexts.
• The vulnerability allows an attacker to impersonate a host to users who set cacerts_path to a CA store that leaves a specific CA out.
• Defenders should evaluate the configuration of cacerts_path and its impact on the system's trust store.
• Updating to version 2.5.2 or later of the hex package may be necessary.

Technical summary

The hex package improperly validates certificates when cacerts_path is set, allowing an attacker to impersonate a host to users who set cacerts_path to a CA store that leaves a specific CA out. This issue affects hex versions from 0.20.2 before 2.5.2. The vulnerability is caused by the package trusting its bundled CA certificates when cacerts_path is set. This can lead to security breaches in systems using the hex package. Defenders should be aware of the potential risks and take necessary actions to mitigate them. The vulnerability can be mitigated by updating to version 2.5.2 or later of the hex package.

Defensive priority

Defenders should prioritize verifying their inventory of systems using hex and assessing exposure based on their specific deployment contexts.

Recommended defensive actions

• Verify the inventory of systems using hex and assess exposure based on specific deployment contexts.
• Evaluate the configuration of cacerts_path and its impact on the system's trust store.
• Consider updating to version 2.5.2 or later of the hex package.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The vulnerability is caused by improper certificate validation in the hex package. When cacerts_path is set, the package trusts its bundled CA certificates, allowing an attacker to impersonate a host if they can intercept HTTPS connections and hold a certificate for a Hex host issued by a CA in Hex's bundled CA store.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.