CVE-2026-47073

Description

Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding. The WebSocket client in src/hackney_ws.erl imposes no upper bound on memory consumption in three code paths. First, read_handshake_response/3 accumulates received bytes into a growing buffer with no size cap; the per-receive timeout resets on every chunk, so a server that streams bytes without ever sending \r\n\r\n causes the buffer to grow until memory is exhausted. Second, parse_payload/9 and parse_active_payload/8 do not validate the declared frame payload length against any limit; because RFC 6455 allows payload lengths up to 2^63-1 bytes, a server that announces a very large frame and dribbles bytes causes the accumulation buffer to grow until OOM. Third, the frag_buffer field in #ws_data{} accumulates continuation frames indefinitely; a server that sends an endless stream of non-final (nofin) fragmented frames without ever sending a final (fin) frame grows frag_buffer without bound. In all three cases the attacker only needs to control the WebSocket server the hackney client connects to, with no authentication or special client configuration required. This issue affects hackney: from 2.0.0 before 4.0.1.

CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0009

Probability of exploitation

0.25%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

Affected Products

Vendor	Product	Versions
benoitc	hackney	2.0.0 — 4.0.1

References

Advisories & Patches

https://cna.erlef.org/cves/CVE-2026-47073.html https://github.com/benoitc/hackney/commit/ce0109e2970ace6e20ff29bae9d05c3ac22ec6dc https://github.com/benoitc/hackney/security/advisories/GHSA-q8jg-fgj4-fphf https://osv.dev/vulnerability/EEF-CVE-2026-47073 https://github.com/benoitc/hackney/security/advisories/GHSA-q8jg-fgj4-fphf

Exploits

https://github.com/benoitc/hackney/security/advisories/GHSA-q8jg-fgj4-fphf https://github.com/benoitc/hackney/security/advisories/GHSA-q8jg-fgj4-fphf

Frequently Asked Questions

What is CVE-2026-47073? +

Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding. The WebSocket client in src/hackney_ws.erl imposes no upper bound on memory consumption in three code paths. First, read_handshake_response/3 accumulates received bytes into a growing buffer with no size cap; the per-receive timeout resets on every chunk, so a server that streams bytes without ever sending \r\n\r\n causes the buffer to grow until memory is exhausted. Second, parse_payload/9 and parse_active_payload/8 do not validate the declared frame payload length against any limit; because RFC 6455 allows payload lengths up to 2^63-1 bytes, a server that announces a very large frame and dribbles bytes causes the accumulation buffer to grow until OOM. Third, the frag_buffer field in #ws_data{} accumulates continuation frames indefinitely; a server that sends an endless stream of non-final (nofin) fragmented frames without ever sending a final (fin) frame grows frag_buffer without bound. In all three cases the attacker only needs to control the WebSocket server the hackney client connects to, with no authentication or special client configuration required. This issue affects hackney: from 2.0.0 before 4.0.1. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-47073? +

CVE-2026-47073 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0009, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-47073? +

CVE-2026-47073 affects products from benoitc, specifically: hackney. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-47073? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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