Vulnerability Description
Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee forward progress. When parse_token/2 receives a non-token, non-whitespace, non-comma byte (e.g. !, @, =, ;), it returns the input unchanged. skip_comma/1 also returns the buffer unchanged when the first byte is not a comma. parse_entries/2 then recurses with identical data, creating a tight infinite tail-recursive loop that pins a scheduler at 100% CPU. The calling process never returns. The entry point parse_and_cache/3 is called synchronously in the connection process on every HTTP response. A single-byte Alt-Svc: ! response header is sufficient to trigger the hang; the header is fully controlled by any HTTP origin the client connects to. This issue affects hackney: from 2.0.0-beta.1 before 4.0.1.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Benoitc | Hackney | >= 2.0.0, < 4.0.1 |
Related Weaknesses (CWE)
References
- https://cna.erlef.org/cves/CVE-2026-47066.htmlPatchThird Party Advisory
- https://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c018Patch
- https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2jExploitPatchVendor Advisory
- https://osv.dev/vulnerability/EEF-CVE-2026-47066PatchThird Party Advisory
- https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2jExploitPatchVendor Advisory
FAQ
What is CVE-2026-47066?
CVE-2026-47066 is a vulnerability with a CVSS score of 7.5 (HIGH). Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee for...
How severe is CVE-2026-47066?
CVE-2026-47066 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-47066?
Check the references section above for vendor advisories and patch information. Affected products include: Benoitc Hackney.