CVE-2026-47066: Benoitc Hackney denial of service (CVSS 7.5)

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Benoitc Hackney≥ 2.0.0 < 4.0.1

Remediation

Fixed in

Benoitc Hackney≥ 4.0.1

Patch & vendor advisories

References

https://cna.erlef.org/cves/CVE-2026-47066.htmlPatchThird Party Advisory
https://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894Patch
https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2jExploitPatchVendor Advisory
https://osv.dev/vulnerability/EEF-CVE-2026-47066PatchThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-47066 being actively exploited?

CVE-2026-47066 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.70%.

How severe is CVE-2026-47066?

CVE-2026-47066 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.70% probability of exploitation.

Which products are affected by CVE-2026-47066?

Affected products include Benoitc Hackney.

How do I fix CVE-2026-47066?

Upgrade affected software to a fixed version, for example Benoitc Hackney 4.0.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-47066 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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