CVE-2026-103503

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.

CVSS

No CVSS.

References

Link	Resource
https://cna.erlef.org/cves/CVE-2026-103503.html
https://github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785
https://github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8
https://github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7
https://github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr
https://osv.dev/vulnerability/EEF-CVE-2026-103503

Configurations

No configuration.

History

12 Oct 2026, 16:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-12 16:17

Updated : 2026-10-16 18:17

NVD link : CVE-2026-103503

Mitre link : CVE-2026-103503

CVE.ORG link : CVE-2026-103503

JSON object : View

Products Affected

No product.

CWE

CWE-295

Improper Certificate Validation

{"id": "CVE-2026-103503", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-103503", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-10-16T17:30:53.768172Z"}}], "cvssMetricV40": [{"type": "Secondary", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "cvssData": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 5.9, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "valueDensity": "NOT_DEFINED", "vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "userInteraction": "ACTIVE", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "LOW", "integrityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "availabilityRequirement": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED"}}]}, "affected": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "affectedData": [{"cpes": ["cpe:2.3:a:hexpm:hex:*:*:*:*:*:*:*:*"], "repo": "https://github.com/hexpm/hex", "vendor": "hexpm", "modules": ["'Elixir.Hex.HTTP.SSL'"], "product": "hex", "versions": [{"status": "affected", "version": "0.20.2", "lessThan": "2.5.2", "versionType": "semver"}], "packageURL": "pkg:otp/hex?repository_url=https:%2F%2Fgithub.com%2Fhexpm%2Fhex&vcs_url=repository_url=git%2Bhttps:%2F%2Fgithub.com%2Fhexpm%2Fhex.git", "packageName": "hex", "programFiles": ["lib/hex/http/ssl.ex"], "defaultStatus": "unaffected", "programRoutines": [{"name": "'Elixir.Hex.HTTP.SSL':ssl_opts/1"}, {"name": "'Elixir.Hex.HTTP.SSL':partial_chain/2"}]}, {"cpes": ["cpe:2.3:a:hexpm:hex:*:*:*:*:*:*:*:*"], "repo": "https://github.com/hexpm/hex", "vendor": "hexpm", "modules": ["'Elixir.Hex.HTTP.SSL'"], "product": "hex", "versions": [{"status": "affected", "changes": [{"at": "5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785", "status": "unaffected"}, {"at": "6232a6498015e559743bec4f4fbec9138837cec8", "status": "unaffected"}], "version": "c9b26a46928bfcd546773571e09c1d05f4cd9fb7", "lessThan": "*", "versionType": "git"}], "packageURL": "pkg:github/hexpm/hex", "packageName": "hexpm/hex", "programFiles": ["lib/hex/http/ssl.ex"], "collectionURL": "https://github.com", "defaultStatus": "unaffected", "programRoutines": [{"name": "'Elixir.Hex.HTTP.SSL':ssl_opts/1"}, {"name": "'Elixir.Hex.HTTP.SSL':partial_chain/2"}]}]}], "published": "2026-10-12T16:17:02.427", "references": [{"url": "https://cna.erlef.org/cves/CVE-2026-103503.html", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://osv.dev/vulnerability/EEF-CVE-2026-103503", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "vulnStatus": "Deferred", "weaknesses": [{"type": "Secondary", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "description": [{"lang": "en", "value": "CWE-295"}]}], "descriptions": [{"lang": "en", "value": "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.\n\ncacerts_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.\n\nThis issue affects hex: from 0.20.2 before 2.5.2."}], "lastModified": "2026-10-16T18:17:18.037", "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}