CVE-2026-47076
published 2026-05-25CVE-2026-47076: Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the…
PriorityP433medium6.5CVSS 3.1
AVLACLPRLUINSCCHINAN
EPSS
0.20%
10.2th percentile
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.
Affected
4 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| benoitc | hackney | >= 0.13.0 < 4.0.1 | 4.0.1 |
| benoitc | hackney | >= 0.13.0 < 4.0.1 | 4.0.1 |
| benoitc | hackney | >= 0.13.0 < 4.0.1 | 4.0.1 |
| benoitc | hackney | >= 4d725507588942fd00efca15b86da3273656510a < 452620a92ec1da2e6b4862a049a2a4f04b42068f | 452620a92ec1da2e6b4862a049a2a4f04b42068f |
CVSS provenance
nvdv3.16.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
nvdv4.06.9MEDIUMCVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/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
cvelistv5v4.06.9MEDIUMCVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
ghsa6.5MEDIUM
Stop checking back — get the weekly exploitation signal.
Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
GHSA
Hackney has SSRF allowlist bypass in hackney_url:normalize/2 via percent-encoded host
ghsa·2026-06-26·CVSS 6.5
CVE-2026-47076 [MEDIUM] CWE-436 Hackney has SSRF allowlist bypass in hackney_url:normalize/2 via percent-encoded host
Hackney has SSRF allowlist bypass in hackney_url:normalize/2 via percent-encoded host
### Summary
`hackney_url:normalize/2` URL-decodes the host component of a parsed URL, but the caller's SSRF allowlist runs before normalization using OTP's `uri_string:parse/1` and `inet:parse_address/1`, neither of which decodes percent-escapes in hostnames. A URL like `http://%31%32%37%2E%30%2E%30%2E%31/` presents an encoded, non-IP-looking host to the validator, which passes the allowlist check; hackney's normalizer then decodes it to `127.0.0.1` and connects to loopback. Because `hackney:request/5` always calls `normalize/2` with no opt-out, every request path that accepts a binary or list URL is affected. This is a parser-differential SSRF in the same class as CVE-2025-1211, but in a different func
VulDB
benoitc hackney up to 4.0.0 interpretation conflict (GHSA-pj7v-xfvx-wmjq / EUVD-2026-31689)
vuldb·2026-05-25
CVE-2026-47076 [LOW] benoitc hackney up to 4.0.0 interpretation conflict (GHSA-pj7v-xfvx-wmjq / EUVD-2026-31689)
A vulnerability was found in benoitc hackney up to 4.0.0. It has been rated as problematic. This vulnerability affects unknown code. This manipulation causes interpretation conflict.
This vulnerability appears as CVE-2026-47076. The attack requires local access. There is no available exploit.
Upgrading the affected component is advised.
CVEList
SSRF allowlist bypass via percent-encoded host in hackney
cvelistv5·2026-05-25·CVSS 6.9
CVE-2026-47076 [MEDIUM] CWE-436 SSRF allowlist bypass via percent-encoded host in hackney
SSRF allowlist bypass via percent-encoded host in hackney
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 techniqu
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
https://cna.erlef.org/cves/CVE-2026-47076.htmlhttps://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068fhttps://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjqhttps://osv.dev/vulnerability/EEF-CVE-2026-47076https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq
2026-05-25
Published