CVE-2026-47066
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
hackneyHex | >= 2.0.0, < 4.0.1 | 4.0.1 |
Affected products
3Patches
Vulnerability mechanics
References
6- cna.erlef.org/cves/CVE-2026-47066.htmlnvdPatchThird Party AdvisoryWEB
- github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894nvdPatchWEB
- osv.dev/vulnerability/EEF-CVE-2026-47066nvdPatchThird Party AdvisoryWEB
- github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2jnvdExploitPatchVendor AdvisoryWEB
- github.com/advisories/GHSA-6cp8-v795-jr2jghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-47066ghsaADVISORY
News mentions
1- Hackney HTTP Client: Ten CVEs Disclosed in a Single Batch — CRLF Injection, Resource Exhaustion, and MoreVypr Intelligence · May 25, 2026