Allocation of Resources Without Limits or Throttling Affecting hackney package, versions >=2.0.0-beta.1 <4.0.1
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-HEX-HACKNEY-16877833
- published26 May 2026
- disclosed25 May 2026
- creditPJUllrich
Introduced: 25 May 2026
NewCVE-2026-47077 (opens in a new tab)How to fix?
Upgrade hackney to version 4.0.1 or higher.
Overview
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling through the await_response_loop in the HTTP/3 client. An attacker can keep a request hanging and exhaust heap memory by dribbling small response chunks just before each per-chunk timeout while the client buffers the entire body. This leaves applications using the non-streaming HTTP/3 response path stuck waiting indefinitely and eventually killed by out-of-memory conditions.
Workarounds
- Use the streaming API for very large HTTP/3 responses instead of the non-streaming
hackney_h3response path, so the client does not buffer the whole body in memory and is less exposed to heap exhaustion from slow-drip responses. - Set the
max_body_sizeoption on HTTP/3 requests to a finite limit, so a peer cannot keep appending data indefinitely and drive the process to out-of-memory.