# CVE-2026-47067: benoitc hackney atom table exhaustion in URL parser

Source: https://junglewise.ai/threats/cve-2026-47067-benoitc-hackney-atom-table-exhaustion-in-url-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-25. Updated: 2026-06-26  
License: CC BY 4.0 with a link back

CVE-2026-47067 · Severity: high · CVSS 8.7 · Published 2026-05-25

Hackney, a popular Erlang HTTP client library, is vulnerable to a denial-of-service attack that can crash the entire application environment. By providing URLs with unique or unrecognized prefixes (like "customscheme://"), an attacker can exhaust the system's internal memory table for "atoms," which are never cleaned up. This can lead to a complete service outage, requiring a full manual restart of the affected server.

Technologies: [Benoit Chesneau Hackney](https://junglewise.ai/threats/technologies/hackney). Vendors: [Benoit Chesneau](https://junglewise.ai/threats/vendors/benoit-chesneau).

## Quick answers

**Is CVE-2026-47067 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47067 being exploited in the wild.

**How severe is CVE-2026-47067?** High severity, with a CVSS score of 8.7, published 25 May 2026.

**Which products and versions are affected?** Benoit Chesneau Hackney >= 2.0.0, < 4.0.1.

**Is there a fix for CVE-2026-47067?** A patch was published on 2026-06-26: Version 4.0.1 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-47067 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-47067?** Check whether you run Benoit Chesneau Hackney at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An atom table exhaustion vulnerability (CWE-770) exists in hackney's URL parser (src/hackney_url.erl). The function hackney_url:parse_url/1 extracts the scheme from a URL and converts it into a BEAM atom using binary_to_atom/2. Since BEAM atoms are not garbage-collected and have a default limit of 1,048,576, an attacker can provide a large number of unique schemes via direct request targets, webhooks, or 'Location' headers in redirect chains. Once the limit is reached, the VM terminates with a 'system_limit' error. This is fixed in version 4.0.1.

## Affected products

- benoitc hackney >= 2.0.0, < 4.0.1

## Identifiers

- CVE-2026-47067
- GHSA-9653-rcfr-5c62

## Timeline

- 2026-05-25: disclosed
- 2026-06-26: advisory: GitHub Advisory published
- 2026-06-26: patched: Version 4.0.1 released

## References

- [https://api.github.com/users/PJUllrich](https://api.github.com/users/PJUllrich)
- [https://github.com/PJUllrich](https://github.com/PJUllrich)
- [https://api.github.com/users/PJUllrich/gists%7B/gist_id%7D](https://api.github.com/users/PJUllrich/gists%7B/gist_id%7D)
- [https://api.github.com/users/PJUllrich/repos](https://api.github.com/users/PJUllrich/repos)
- [https://avatars.githubusercontent.com/u/10426523?v=4](https://avatars.githubusercontent.com/u/10426523?v=4)
- [https://api.github.com/users/PJUllrich/events%7B/privacy%7D](https://api.github.com/users/PJUllrich/events%7B/privacy%7D)

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