Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackneyurl:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackneyurl{} record. OTP's uristring:parse/1 and inet:parseaddress/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.
{
"cna_assigner": "EEF",
"unresolved_ranges": [
{
"source": "AFFECTED_FIELD",
"extracted_events": [
{
"introduced": "4d725507588942fd00efca15b86da3273656510a"
},
{
"fixed": "452620a92ec1da2e6b4862a049a2a4f04b42068f"
}
]
}
],
"cwe_ids": [
"CWE-436",
"CWE-918"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47076.json"
}