What is CVE-2026-103503?

CVE-2026-103503 is Hex trusts its bundled CA certificates when cacerts_path is set. The supplied enrichment data classifies it as Cryptography mapped to CWE-295 CWE-295.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-103503. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-103503 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

1 public PoC repositories reported; 0 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-103503 using CVSS 5.9, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

Workarounds are not confirmed from current sources. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

mediumCryptographypublic exploit

CVE-2026-103503

CVE-2026-103503 — Hex trusts its bundled CA certificates when cacerts_path is set

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.

Published Oct 12, 2026Updated Oct 12, 2026Sources: NVD, hexpm (CNA), GitHub, Red Hat (VEX), SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

ahead of 0% of scored CVEs

Affects

hexpm

2 products listed

CVSS base

5.9

medium · 2 sources

Remediation

The vendor's own words where we have them.

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.

Red Hat VEX · CVE-2026-103503

fixed0affected0not affected1

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
hexpm	hex	0.20.2 to < 2.5.2	Vulnerable
hexpm	hex	c9b26a46928bfcd546773571e09c1d05f4cd9fb7	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Scope

Attack Complexity

High

Attack Vector

Network

Privileges Req

None

User Interaction

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
5.9	CVSS 4.0	medium	—	—	hexpm (CNA)
6.8	CVSS 3.1	medium	—	—	Red Hat (VEX)

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-295 · Improper Certificate Validation

Bypass Protection Mechanism
Gain Privileges or Assume Identity::

Mitigation: Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.

Weakness & attack patterns

CWE-295

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-475 · Signature Spoofing by Improper ValidationCAPEC-459 · Creating a Rogue Certification Authority Certificate

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Search application, proxy, and WAF logs for requests touching /1, /2.
Prioritize edge telemetry for network-reachable hex.
Monitor for scanner or exploit-pattern traffic after 1 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 5.9 (AV:N)
Oct 12, 2026 · NVD
Initial · CVE published
Oct 12, 2026 · NVD
CVE published by MITRE.
Oct 12, 2026 · SOCRadar CTI

References

8 on the record

cna.erlef.org/cves/CVE-2026-103503.html
Vendor Advisory, Mitre, NIST
github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785
Exploit, Third Party Advisory, Mitre, NIST
github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8
Exploit, Third Party Advisory, Mitre, NIST
github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7
Exploit, Third Party Advisory, Mitre, NIST
github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr
Exploit, Third Party Advisory, Mitre, NIST
osv.dev/vulnerability/EEF-CVE-2026-103503
Vendor Advisory, Mitre, NIST
access.redhat.com/security/cve/CVE-2026-103503
Vendor Advisory
www.cve.org/CVERecord?id=CVE-2026-103503
Vendor Advisory

Elsewhere on this site

hexpmevery CVE for this vendor
Cryptographysame class
CWE-295other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-103503 is Hex trusts its bundled CA certificates when cacerts_path is set, a medium vulnerability affecting hex from hexpm. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-103503. Public exploit evidence is: 1 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 5.9 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.