{"id":"CVE-2026-47076","state":"PUBLISHED","title":"SSRF allowlist bypass via percent-encoded host in hackney","description":"Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP's uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller's allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney's normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost.\n\nThis issue affects hackney: from 0.13.0 before 4.0.1.","publishedAt":"2026-05-25T14:00:46.707Z","updatedAt":"2026-05-27T15:41:17.845Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N","source":"EEF"},"assigner":"EEF","products":["benoitc hackney"],"affected":[{"vendor":"benoitc","product":"hackney","packageName":"hackney","packageURL":"pkg:hex/hackney","defaultStatus":"unaffected","versions":[{"version":"0.13.0","status":"affected","lessThan":"4.0.1","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"],"modules":["hackney_url"],"programFiles":["src/hackney_url.erl"],"programRoutines":[{"name":"hackney_url:normalize/2"}],"repo":"https://github.com/benoitc/hackney"},{"vendor":"benoitc","product":"hackney","packageName":"benoitc/hackney","packageURL":"pkg:github/benoitc/hackney","defaultStatus":"unaffected","versions":[{"version":"4d725507588942fd00efca15b86da3273656510a","status":"affected","lessThan":"452620a92ec1da2e6b4862a049a2a4f04b42068f","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"],"modules":["hackney_url"],"programFiles":["src/hackney_url.erl"],"programRoutines":[{"name":"hackney_url:normalize/2"}],"repo":"https://github.com/benoitc/hackney"}],"references":["https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq","https://cna.erlef.org/cves/CVE-2026-47076.html","https://osv.dev/vulnerability/EEF-CVE-2026-47076","https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f"],"weaknesses":["CWE-436","CWE-918"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/47xxx/CVE-2026-47076.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-47076","state":"PUBLISHED","datePublished":"2026-05-25T14:00:46.707Z","dateUpdated":"2026-05-27T15:41:17.845Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-05-18T17:28:10.319Z"},"containers":{"cna":{"title":"SSRF allowlist bypass via percent-encoded host in hackney","descriptions":[{"lang":"en","value":"Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP's uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller's allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney's normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost.\n\nThis issue affects hackney: from 0.13.0 before 4.0.1."}],"affected":[{"vendor":"benoitc","product":"hackney","packageName":"hackney","packageURL":"pkg:hex/hackney","defaultStatus":"unaffected","versions":[{"version":"0.13.0","status":"affected","lessThan":"4.0.1","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"],"modules":["hackney_url"],"programFiles":["src/hackney_url.erl"],"programRoutines":[{"name":"hackney_url:normalize/2"}],"repo":"https://github.com/benoitc/hackney"},{"vendor":"benoitc","product":"hackney","packageName":"benoitc/hackney","packageURL":"pkg:github/benoitc/hackney","defaultStatus":"unaffected","versions":[{"version":"4d725507588942fd00efca15b86da3273656510a","status":"affected","lessThan":"452620a92ec1da2e6b4862a049a2a4f04b42068f","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"],"modules":["hackney_url"],"programFiles":["src/hackney_url.erl"],"programRoutines":[{"name":"hackney_url:normalize/2"}],"repo":"https://github.com/benoitc/hackney"}],"references":[{"url":"https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-47076.html","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-47076","tags":["related"]},{"url":"https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f","tags":["patch"]}],"metrics":[{"cvssV4_0":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"LOCAL","baseScore":6.9,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"HIGH","subIntegrityImpact":"NONE","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"NONE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-436","description":"CWE-436 Interpretation Conflict","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-918","description":"CWE-918 Server-Side Request Forgery (SSRF)","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-05-27T15:41:17.845Z"},"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*","versionEndExcluding":"4.0.1","versionStartIncluding":"0.13.0","vulnerable":true}],"negate":false,"operator":"AND"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Ganbagana"},{"lang":"en","type":"remediation developer","value":"Benoit Chesneau"},{"lang":"en","type":"analyst","value":"Jonatan Männchen / EEF"}],"impacts":[{"capecId":"CAPEC-664","descriptions":[{"lang":"en","value":"CAPEC-664 Server Side Request Forgery"}]}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-26T15:46:49.956392Z","id":"CVE-2026-47076","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-26T15:46:52.424Z"}}]}}}