PT-2026-43064 · Benoitc · Hackney

Benoit Chesneau + 2 · Published 2026-05-25 · Updated 2026-05-25 · CVE-2026-47066

Mitre

CVSS v4.0

8.7

High

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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.

Fix

Infinite Loop

Weakness Enumeration

CWE-835

Related Identifiers

CVE-2026-47066

Affected Products

Hackney

References · 4

• https://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894 · Patch
• https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2j · Vendor Advisory
• https://osv.dev/vulnerability/EEF-CVE-2026-47066 · Note
• https://cna.erlef.org/cves/CVE-2026-47066.html · Note