{"id":"CVE-2026-115700","state":"PUBLISHED","title":"SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney","description":"Interpretation Conflict vulnerability in hackney_url in benoitc hackney allows Server Side Request Forgery via a percent-encoded bracketed IPv6 literal or an IP literal with a trailing dot. A host such as %5B%3A%3Affff%3A127%2E0%2E0%2E1%5D (decoding to [::ffff:127.0.0.1]) or 127.0.0.1. is not an IP address to a caller's allowlist built on uri_string:parse/1 and inet:parse_address/1, while hackney connects to the address it denotes. The same applies to a Location target when redirects are followed.\n\nThe IP-literal gate that hackney_url:normalize/2 applies to a percent-decoded host, added to close the percent-encoded IP bypass of CVE-2026-47076, passes the decoded value to inet_parse:address/1 as is. The connect path in hackney_happy:parse_address/1 drops a surrounding bracket pair, and the resolver ignores a trailing dot, so both forms pass the gate and still reach the literal address. Domain names with a trailing dot and unencoded IPv6 literals are not affected.\n\nThis issue affects hackney: from 4.0.1 before 4.9.0.","publishedAt":"2026-10-26T13:49:02.744Z","updatedAt":"2026-10-26T13:49:02.744Z","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":"4.0.1","status":"affected","lessThan":"4.9.0","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":"452620a92ec1da2e6b4862a049a2a4f04b42068f","status":"affected","lessThan":"f19561a0b422376348c91537e51377ab7325f4ee","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/releases/tag/4.9.0","https://cna.erlef.org/cves/CVE-2026-115700.html","https://osv.dev/vulnerability/EEF-CVE-2026-115700","https://github.com/benoitc/hackney/pull/987","https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f","https://github.com/benoitc/hackney/commit/f19561a0b422376348c91537e51377ab7325f4ee"],"weaknesses":["CWE-436","CWE-918"],"ingestedAt":"2026-10-29T20:10:43.281Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/115xxx/CVE-2026-115700.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-115700","state":"PUBLISHED","datePublished":"2026-10-26T13:49:02.744Z","dateUpdated":"2026-10-26T13:49:02.744Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-10-25T17:30:02.231Z"},"containers":{"cna":{"title":"SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney","descriptions":[{"lang":"en","value":"Interpretation Conflict vulnerability in hackney_url in benoitc hackney allows Server Side Request Forgery via a percent-encoded bracketed IPv6 literal or an IP literal with a trailing dot. A host such as %5B%3A%3Affff%3A127%2E0%2E0%2E1%5D (decoding to [::ffff:127.0.0.1]) or 127.0.0.1. is not an IP address to a caller's allowlist built on uri_string:parse/1 and inet:parse_address/1, while hackney connects to the address it denotes. The same applies to a Location target when redirects are followed.\n\nThe IP-literal gate that hackney_url:normalize/2 applies to a percent-decoded host, added to close the percent-encoded IP bypass of CVE-2026-47076, passes the decoded value to inet_parse:address/1 as is. The connect path in hackney_happy:parse_address/1 drops a surrounding bracket pair, and the resolver ignores a trailing dot, so both forms pass the gate and still reach the literal address. Domain names with a trailing dot and unencoded IPv6 literals are not affected.\n\nThis issue affects hackney: from 4.0.1 before 4.9.0."}],"affected":[{"vendor":"benoitc","product":"hackney","packageName":"hackney","packageURL":"pkg:hex/hackney","defaultStatus":"unaffected","versions":[{"version":"4.0.1","status":"affected","lessThan":"4.9.0","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":"452620a92ec1da2e6b4862a049a2a4f04b42068f","status":"affected","lessThan":"f19561a0b422376348c91537e51377ab7325f4ee","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/releases/tag/4.9.0","name":"hackney 4.9.0 release notes","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-115700.html","name":"EEF CNA record for CVE-2026-115700","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-115700","name":"OSV record EEF-CVE-2026-115700","tags":["related"]},{"url":"https://github.com/benoitc/hackney/pull/987","name":"Refuse bracketed and trailing-dot IP literals in normalize/2 (benoitc/hackney#987)","tags":["related"]},{"url":"https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f","name":"Introducing commit 452620a in benoitc/hackney","tags":["related"]},{"url":"https://github.com/benoitc/hackney/commit/f19561a0b422376348c91537e51377ab7325f4ee","name":"Fix commit f19561a in benoitc/hackney","tags":["patch"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"LOCAL","baseScore":6.9,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"HIGH","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","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","vulnerabilityResponseEffort":"NOT_DEFINED"},"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":"2026-10-26T13:49:02.744Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

The application passes URLs that an untrusted party can influence to hackney and relies on its own host allowlist, built on uri_string:parse/1 or inet:parse_address/1, to keep requests away from internal addresses.

"},{"base64":false,"type":"text/markdown","value":"The application passes URLs that an untrusted party can influence to hackney and relies on its own host allowlist, built on `uri_string:parse/1` or `inet:parse_address/1`, to keep requests away from internal addresses."}],"value":"The application passes URLs that an untrusted party can influence to hackney and relies on its own host allowlist, built on uri_string:parse/1 or inet:parse_address/1, to keep requests away from internal addresses."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*","versionEndExcluding":"4.9.0","versionStartIncluding":"4.0.1","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Eurico Nicacio"},{"lang":"en","type":"reporter","value":"Eurico Nicacio"},{"lang":"en","type":"remediation developer","value":"Benoit Chesneau"},{"lang":"en","type":"coordinator","value":"Jonatan Männchen / EEF"}],"dateAssigned":"2026-10-26T10:12:09.000Z","datePublic":"2026-10-25T00:00:00.000Z","impacts":[{"capecId":"CAPEC-664","descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

An application that checks user-supplied URLs against an IP allowlist before handing them to hackney can be made to request loopback, link-local metadata and private-network addresses that the allowlist rejects when they are written plainly.

"},{"base64":false,"type":"text/markdown","value":"An application that checks user-supplied URLs against an IP allowlist before handing them to hackney can be made to request loopback, link-local metadata and private-network addresses that the allowlist rejects when they are written plainly."}],"value":"An application that checks user-supplied URLs against an IP allowlist before handing them to hackney can be made to request loopback, link-local metadata and private-network addresses that the allowlist rejects when they are written plainly."}]}],"source":{"discovery":"EXTERNAL"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

Run the allowlist on the host that hackney_url:normalize/1 returns for the parsed URL, and strip a surrounding bracket pair and a trailing dot from it before the IP check, so the check sees the same address the connect path uses.

"},{"base64":false,"type":"text/markdown","value":"Run the allowlist on the host that `hackney_url:normalize/1` returns for the parsed URL, and strip a surrounding bracket pair and a trailing dot from it before the IP check, so the check sees the same address the connect path uses."}],"value":"Run the allowlist on the host that hackney_url:normalize/1 returns for the parsed URL, and strip a surrounding bracket pair and a trailing dot from it before the IP check, so the check sees the same address the connect path uses."}],"x_technicalAnalysis":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

1. The gate. hackney_url:normalize/2 in src/hackney_url.erl percent-decodes a host that is not already an IP literal and raises invalid_url_host when inet_parse:address/1 accepts the decoded value. This closed the plain percent-encoded IP case.

\n

2. What the connect path accepts. hackney_happy:parse_address/1 removes a surrounding [...] pair before calling inet:parse_address/1, and the resolver treats a trailing dot as the root label. Neither form is accepted by inet_parse:address/1, so [::ffff:127.0.0.1] and 127.0.0.1. pass the gate.

\n

3. Result. A percent-encoded bracketed IPv6 literal such as %5B%3A%3Affff%3A127%2E0%2E0%2E1%5D, or an IPv4 literal with a trailing dot, is not an IP address to a caller's check based on uri_string:parse/1 and inet:parse_address/1, but hackney connects to the address it denotes. The same applies to a Location target when redirects are followed. The fix strips one bracket pair and one trailing dot in ip_candidate/1 before the gate.

"},{"base64":false,"type":"text/markdown","value":"**1. The gate.** `hackney_url:normalize/2` in `src/hackney_url.erl` percent-decodes a host that is not already an IP literal and raises `invalid_url_host` when `inet_parse:address/1` accepts the decoded value. This closed the plain percent-encoded IP case.\n\n**2. What the connect path accepts.** `hackney_happy:parse_address/1` removes a surrounding `[...]` pair before calling `inet:parse_address/1`, and the resolver treats a trailing dot as the root label. Neither form is accepted by `inet_parse:address/1`, so `[::ffff:127.0.0.1]` and `127.0.0.1.` pass the gate.\n\n**3. Result.** A percent-encoded bracketed IPv6 literal such as `%5B%3A%3Affff%3A127%2E0%2E0%2E1%5D`, or an IPv4 literal with a trailing dot, is not an IP address to a caller's check based on `uri_string:parse/1` and `inet:parse_address/1`, but hackney connects to the address it denotes. The same applies to a `Location` target when redirects are followed. The fix strips one bracket pair and one trailing dot in `ip_candidate/1` before the gate."}],"value":"1. The gate. hackney_url:normalize/2 in src/hackney_url.erl percent-decodes a host that is not already an IP literal and raises invalid_url_host when inet_parse:address/1 accepts the decoded value. This closed the plain percent-encoded IP case.\n\n2. What the connect path accepts. hackney_happy:parse_address/1 removes a surrounding [...] pair before calling inet:parse_address/1, and the resolver treats a trailing dot as the root label. Neither form is accepted by inet_parse:address/1, so [::ffff:127.0.0.1] and 127.0.0.1. pass the gate.\n\n3. Result. A percent-encoded bracketed IPv6 literal such as %5B%3A%3Affff%3A127%2E0%2E0%2E1%5D, or an IPv4 literal with a trailing dot, is not an IP address to a caller's check based on uri_string:parse/1 and inet:parse_address/1, but hackney connects to the address it denotes. The same applies to a Location target when redirects are followed. The fix strips one bracket pair and one trailing dot in ip_candidate/1 before the gate."}]}}}}