CVE-2026-47071 SOCKS5 TLS upgrade ignores caller timeout in hackney
A hostile SOCKS5 proxy can cause indefinite blocking in hackney by stalling the TLS handshake, ignoring caller-supplied timeouts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47071?
CVE-2026-47071 is a high-severity denial of service vulnerability in benoitc hackney, published on 25 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Uncontrolled Resource Consumption vulnerability in benoitc hackney allows Flooding. The SOCKS5 transport in src/hackney_socks5.erl correctly applies the caller-supplied timeout to the SOCKS5 negotiation phase, but then upgrades the connection to TLS using the two-argument form ssl:connect/2, which defaults to an infinite timeout. The Timeout value is in scope at the call site but is not forwarded. A hostile SOCKS5 proxy that completes the SOCKS5 handshake normally and then goes silent (or sends a partial TLS ServerHello and stalls) will cause the connecting process to block indefinitely, regardless of the connect_timeout or recv_timeout options supplied by the caller.
This issue affects hackney: from 0.10.0 before 4.0.1.
Weakness: CWE-400
Which versions are affected by CVE-2026-47071?
3 open source packages ship an affected version, including hackney. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hackney Hex | From 0.10.0 | 4.0.1 |
hackney Hex | From 0.10.0 | 4.0.1 |
hackney Hex | From 0.10.0 | 4.0.1 |
Products include Benoitc Hackney.
How do I fix CVE-2026-47071?
Upgrade hackney to 4.0.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-47071 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47071 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-2026-47077 Unbounded body accumulation in HTTP/3 response loop in hackney
- CVE-2026-47072 CRLF injection in WebSocket upgrade request in hackney
Sources
Also known as EEF-CVE-2026-47071, GHSA-gp9c-pm5m-5cxr.