CVE-2026-47077 Unbounded body accumulation in HTTP/3 response loop in hackney
A malicious HTTP/3 server can cause an out-of-memory denial of service in the hackney library by sending slow, unbounded response chunks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47077?
CVE-2026-47077 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
Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding. hackney_h3:await_response_loop/6 accumulates the HTTP/3 response body in memory without any size cap. The after Timeout clause is a per-message inactivity timer that resets on every received chunk, housekeeping message, or settings frame — it is not a wall-clock deadline. A malicious HTTP/3 server that emits one small chunk every Timeout - 1 ms with Fin = false and never sends a final frame keeps the loop alive indefinitely while the accumulation buffer grows linearly without bound, eventually exhausting the BEAM process heap and causing an out-of-memory condition.
This issue affects hackney: from 2.0.0 before 4.0.1.
Weakness: CWE-400
Which versions are affected by CVE-2026-47077?
3 open source packages ship an affected version, including hackney. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hackney Hex | From 2.0.0 | 4.0.1 |
hackney Hex | From 2.0.0 | 4.0.1 |
hackney Hex | From 2.0.0 | 4.0.1 |
Products include Benoitc Hackney.
How do I fix CVE-2026-47077?
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-2026-47077 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47077 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-2026-47072 CRLF injection in WebSocket upgrade request in hackney
Sources
Also known as EEF-CVE-2026-47077, GHSA-jq4m-q6p2-8gwc.