CVE-2026-47066Public exploitNetwork attack vector

Connection-process hang via stalled Alt-Svc parsing

Published May 25, 2026 · Updated May 25, 2026

Infinite loop in hackney 2.0.0-beta.1 through 4.0.0 allows remote attackers to hang a connection process via a crafted Alt-Svc header. In hackney_altsvc:parse_entries/2, a failed parse leaves the offending byte unconsumed, and recursion resumes with the identical buffer. Any HTTP origin reached by the client can supply the header without authentication, pinning one Erlang scheduler at full CPU while the calling process never returns.

CVSS severity8.7
High
EPSS probability0.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Infinite loop in hackney 2.0.0-beta.1 through 4.0.0 allows remote attackers to hang a connection process via a crafted Alt-Svc header. In hackney_altsvc:parse_entries/2, a failed parse leaves the offending byte unconsumed, and recursion resumes with the identical buffer. Any HTTP origin reached by the client can supply the header without authentication, pinning one Erlang scheduler at full CPU while the calling process never returns.

The record

CVE
CVE-2026-47066
Published
May 25, 2026
Updated
May 25, 2026
Vendor
Benoit Chesneau
Product
Hackney
Classifications
CWE-835, CAPEC-130, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 25, 2026CVE publishedPublication date reported by the CVE source.
  2. May 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.0.0-beta.1 <4.0.1
  2. Affected versionversion=408e5fe20302226ea8c74dde2bcbd452d712b5b2 <e548aba1f97ffa3f4750da7b772998fb78c01894

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Benoit Chesneau · Hackneyversion=2.0.0-beta.1 <4.0.1; version=408e5fe20302226ea8c74dde2bcbd452d712b5b2 <e548aba1f97ffa3f4750da7b772998fb78c01894

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7EEFCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
CAPEC-130Excessive Allocation
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo