CVE-2026-47067 Atom table exhaustion via unrecognized URL schemes in hackney
An attacker can crash the Erlang VM by exhausting the atom table via unrecognized URL schemes in the hackney library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47067?
CVE-2026-47067 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. The URL parser in src/hackney_url.erl converts every unrecognized URL scheme to a permanent BEAM atom via binary_to_atom/2. BEAM atoms are never garbage-collected and the atom table defaults to a hard limit of 1,048,576 entries. An attacker who can supply URLs with attacker-chosen scheme prefixes — directly as request targets, as configured webhook URLs, or via Location headers followed during redirects — can exhaust the atom table and crash the entire BEAM VM with system_limit.
This issue affects hackney: from 2.0.0 before 4.0.1.
Weakness: CWE-770
Which versions are affected by CVE-2026-47067?
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-2026-47067?
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-2026-47067 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47067 exists.
Other vulnerabilities in benoitc hackney
- CVE-2026-47066 Infinite loop in Alt-Svc header parser 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
- CVE-2026-47072 CRLF injection in WebSocket upgrade request in hackney
Sources
Also known as EEF-CVE-2026-47067, GHSA-9653-rcfr-5c62.