CVE-2026-47076 SSRF allowlist bypass via percent-encoded host in hackney
Attackers can bypass SSRF allowlists in hackney by using percent-encoded hosts, enabling access to internal services and cloud metadata.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47076?
CVE-2026-47076 is a medium-severity server-side request forgery vulnerability in benoitc hackney, published on 25 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
This issue affects hackney: from 0.13.0 before 4.0.1.
Which versions are affected by CVE-2026-47076?
3 open source packages ship an affected version, including hackney. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hackney Hex | From 0.13.0 | 4.0.1 |
hackney Hex | From 0.13.0 | 4.0.1 |
hackney Hex | From 0.13.0 | 4.0.1 |
Products include Benoitc Hackney.
How do I fix CVE-2026-47076?
Upgrade hackney to 4.0.1 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-47076 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47076 exists.
Other vulnerabilities in benoitc hackney
- CVE-2026-47066 Infinite loop in Alt-Svc header parser in hackney
- CVE-2026-47067 Atom table exhaustion via unrecognized URL schemes in hackney
- CVE-2026-47073 Unbounded memory consumption in WebSocket client in hackney
- CVE-2026-47071 SOCKS5 TLS upgrade ignores caller timeout in hackney
- CVE-2026-47077 Unbounded body accumulation in HTTP/3 response loop in hackney
Sources
Also known as EEF-CVE-2026-47076, GHSA-pj7v-xfvx-wmjq.