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TI-2026-34668 Aliases CVE-2026-47066GHSA-6cp8-v795-jr2j

Infinite loop in Alt-Svc header parser in hackney

Priority HIGH 77CWE-835Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-835.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00753 55th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed hackney (benoitc): 4.0.1hackney (Hex): 4.0.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
benoitchackney2.0.0-beta.1 to before 4.0.14.0.1Patch availableCNA
—hackney (Hex)2.0.0 to before 4.0.14.0.1Patch availableGHSA-6cp8-v795-jr2j
  • hackney Vendorbenoitc Affected 2.0.0-beta.1 to before 4.0.1 Fixed in 4.0.1 Patch available CNA
  • hackney (Hex) Vendor— Affected 2.0.0 to before 4.0.1 Fixed in 4.0.1 Patch available GHSA-6cp8-v795-jr2j

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*2.0.0 to before 4.0.1Vulnerablebenoitc
  • cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:* Versions 2.0.0 to before 4.0.1 Vulnerable ·benoitc

Remediation

  • Fix · CNA hackney (benoitc) Fixed in 4.0.1
  • Fix · GHSA-6cp8-v795-jr2j hackney (Hex) Fixed in 4.0.1 Advisory →

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    benoitc hackney 4.0.1

    10 records Highest priority Priority HIGH 6 HIGH, 4 MEDIUM

    Other records, highest priority first

    • TI-2026-34675 Unbounded memory consumption in WebSocket client in hackneyPriority HIGH 77
    • TI-2026-34669 Atom table exhaustion via unrecognized URL schemes in hackneyPriority HIGH 77
    • TI-2026-34679 Unbounded body accumulation in HTTP/3 response loop in hackneyPriority HIGH 75
    Show all 10 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-47066
  2. 2026-10-03 Alias added: GHSA-6cp8-v795-jr2j

References

Exploit 1

Patch 3

Advisory 1

Other 1

  • TI-2026-34675 Unbounded memory consumption in WebSocket client in hackney CVSS 4.0HIGH 8.7
  • TI-2026-34669 Atom table exhaustion via unrecognized URL schemes in hackney CVSS 4.0HIGH 8.7
  • TI-2026-34679 Unbounded body accumulation in HTTP/3 response loop in hackney CVSS 4.0HIGH 8.2
  • TI-2026-34673 SOCKS5 TLS upgrade ignores caller timeout in hackney CVSS 4.0HIGH 8.2
  • TI-2026-34674 CRLF injection in WebSocket upgrade request in hackney CVSS 4.0MEDIUM 6.9
  • TI-2026-34678 SSRF allowlist bypass via percent-encoded host in hackney CVSS 4.0MEDIUM 6.9
See all 9 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences