{"schemaVersion":3,"id":"CVE-2026-103503","aliases":["DEBIAN-CVE-2026-103503","UBUNTU-CVE-2026-103503"],"status":"published","duplicateOf":null,"title":null,"description":"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.","dates":{"published":"2026-10-12T15:17:45.545Z","modified":"2026-10-16T17:32:45.735Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":5.9,"severity":"medium","version":"4.0","versionLabel":"v4.0","source":"NVD","vector":"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","computed":false,"selection":"backend-summary"},"metrics":[{"version":"4.0","versionLabel":"v4.0","source":"NVD","score":5.9,"severity":"medium","vector":"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","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"CVE.org","score":5.9,"severity":"medium","vector":"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","exploitability":null,"impact":null,"computed":false},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Debian","score":5.9,"severity":"medium","vector":"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","exploitability":null,"impact":null,"computed":true},{"version":"4.0","versionLabel":"v4.0","source":"OSV · Ubuntu","score":5.9,"severity":"medium","vector":"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","exploitability":null,"impact":null,"computed":true}]},"epss":{"probability":0.00191,"percentile":0.08269,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-13T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00191,"percentile":0.08269}],"last30":[{"date":"2026-10-13T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00191,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00191,"percentile":0.08269}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-295","name":"Improper Certificate Validation","description":"The product does not validate, or incorrectly validates, a certificate.","type":"weakness","status":"Draft","abstraction":"Base","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/295.html"}],"affected":[{"vendor":"debian","product":"erlang-hex","name":"erlang-hex","label":"erlang-hex","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/erlang-hex","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"erlang-hex","name":"erlang-hex","label":"erlang-hex","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/erlang-hex","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null},{"vendor":"hexpm","product":"hex","name":"hex","label":"hex","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 0.20.2, < 2.5.2","noFixRecorded":false,"fixedIn":null},{"text":"≥ c9b26a46928bfcd546773571e09c1d05f4cd9fb7","noFixRecorded":true,"fixedIn":null}],"versionsText":"≥ 0.20.2, < 2.5.2 | ≥ c9b26a46928bfcd546773571e09c1d05f4cd9fb7 (No fix recorded)","eol":null,"hubHref":"/vendor/hexpm/hex"}],"affectedCount":3,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://cna.erlef.org/cves/CVE-2026-103503.html","label":"cna.erlef.org/cves/CVE-2026-103503.html","hostname":"cna.erlef.org","tags":["Related","REPORT"]},{"url":"https://github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785","label":"github.com/hexpm/hex/commit/5f5a2136c7cf5991b6e8a30d645ca9f8e74b0785","hostname":"github.com","tags":["Patch","REPORT"]},{"url":"https://github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8","label":"github.com/hexpm/hex/commit/6232a6498015e559743bec4f4fbec9138837cec8","hostname":"github.com","tags":["Patch","REPORT"]},{"url":"https://github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7","label":"github.com/hexpm/hex/commit/c9b26a46928bfcd546773571e09c1d05f4cd9fb7","hostname":"github.com","tags":["Related","REPORT"]},{"url":"https://github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr","label":"github.com/hexpm/hex/security/advisories/GHSA-rw8q-hg7m-cxgr","hostname":"github.com","tags":["Related","Vendor Advisory","REPORT"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-103503","label":"osv.dev/vulnerability/EEF-CVE-2026-103503","hostname":"osv.dev","tags":["Related","REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-103503","label":"security-tracker.debian.org/tracker/CVE-2026-103503","hostname":"security-tracker.debian.org","tags":["Advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-103503","label":"ubuntu.com/security/CVE-2026-103503","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-103503","label":"www.cve.org/CVERecord?id=CVE-2026-103503","hostname":"www.cve.org","tags":["REPORT"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-10-12T15:17:45.545Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-10-16T17:32:45.735Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":24,"level":"low","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-19T19:14:49.000Z","stale":false,"partial":false}}