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CVE-2026-47066— Infinite loop in Alt-Svc header parser in hackney

Quick assessment

Affected
benoitc hackney
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Hackney是Hackney公司的一个程序库。 Hackney 2.0.0-beta.1至4.0.1之前版本存在安全漏洞，该漏洞源于Alt-Svc响应头解析器无法保证前向进展，可能导致无限循环和CPU耗尽。

AI Predicted 7.5 Difficulty: Easy EPSS 0.70% · P51

Affected Version Matrix 2

VendorProduct Version RangeStatus
benoitc hackney 2.0.0-beta.1< 4.0.1 affected
408e5fe20302226ea8c74dde2bcbd452d712b5b2< e548aba1f97ffa3f4750da7b772998fb78c01894 affected
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I. Basic Information for CVE-2026-47066

Vulnerability Information
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Vulnerability Title
Infinite loop in Alt-Svc header parser in hackney
Source: CVE Program / CVE List V5
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5
Vulnerability Title
Hackney 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Hackney是Hackney公司的一个程序库。 Hackney 2.0.0-beta.1至4.0.1之前版本存在安全漏洞，该漏洞源于Alt-Svc响应头解析器无法保证前向进展，可能导致无限循环和CPU耗尽。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
benoitc hackney 2.0.0-beta.1 ~ 4.0.1 cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*
benoitc hackney 408e5fe20302226ea8c74dde2bcbd452d712b5b2 ~ e548aba1f97ffa3f4750da7b772998fb78c01894 cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-47066

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III. Intelligence Information for CVE-2026-47066

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Patches & Fixes for CVE-2026-47066 (1)

Vendor Advisories for CVE-2026-47066 (3)

Same Patch Batch · benoitc · 2026-05-25 · 10 CVEs total

CVE-2026-47075 6.8 MEDIUM CR/LF injection in query parameter in hackney
CVE-2026-47070 HTTP/3 redirect handler leaks Authorization and Cookie headers to cross-origin redirect ta
CVE-2026-47069 CRLF injection in cookie domain/path options in hackney
CVE-2026-47076 SSRF allowlist bypass via percent-encoded host in hackney
CVE-2026-47073 Unbounded memory consumption in WebSocket client in hackney
CVE-2026-47072 CRLF injection in WebSocket upgrade request in hackney
CVE-2026-47077 Unbounded body accumulation in HTTP/3 response loop in hackney
CVE-2026-47067 Atom table exhaustion via unrecognized URL schemes in hackney
CVE-2026-47071 SOCKS5 TLS upgrade ignores caller timeout in hackney

IV. Related Vulnerabilities

Same product: hackney
Same vendor: benoitc
Same weakness: CWE-835

V. Comments for CVE-2026-47066

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