{"id":"UBUNTU-CVE-2026-103503","details":"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.","modified":"2026-10-17T12:57:58.505766757Z","published":"2026-10-15T00:00:00Z","upstream":["CVE-2026-103503"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-103503"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-103503"},{"type":"REPORT","url":"https://cna.erlef.org/cves/CVE-2026-103503.html"},{"type":"REPORT","url":"https://github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785"},{"type":"REPORT","url":"https://github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8"},{"type":"REPORT","url":"https://github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7"},{"type":"REPORT","url":"https://github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr"},{"type":"REPORT","url":"https://osv.dev/vulnerability/EEF-CVE-2026-103503"}],"affected":[{"package":{"name":"erlang-hex","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/erlang-hex?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.5-1"],"ecosystem_specific":{"binaries":[{"binary_name":"erlang-hex","binary_version":"2.0.5-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-103503.json"}},{"package":{"name":"erlang-hex","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/erlang-hex?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.6-2build1","2.5.1-2"],"ecosystem_specific":{"binaries":[{"binary_version":"2.5.1-2","binary_name":"erlang-hex"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-103503.json"}},{"package":{"name":"erlang-hex","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/erlang-hex?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.6-2","2.0.6-2build1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.6-2build1","binary_name":"erlang-hex"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-103503.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"},{"type":"Ubuntu","score":"medium"}]}