CVE-2026-47076

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. This issue affects hackney: from 0.13.0 before 4.0.1.

• CWE-436
• CWE-918

• https://cna.erlef.org/cves/CVE-2026-47076.htmlPatch, Third Party Advisory
• https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068fPatch
• https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjqExploit, Patch, Vendor Advisory
• https://osv.dev/vulnerability/EEF-CVE-2026-47076Patch, Third Party Advisory
• https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjqExploit, Patch, Vendor Advisory

Published

May 25, 2026

Last Modified

Jul 24, 2026

Status

Analyzed

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