Unbounded response body buffering in hackney allows memory exhaustion
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- 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. Impact type from CWE-770.
Summary
Hackney from 2.0.0-beta.1 before 4.9.0 buffers the whole HTTP response body without any size limit, a resource allocation flaw (CWE-770). A malicious HTTP server that the client requests can send an oversized or highly compressed body, exhausting the client's memory. With auto-decompression enabled, the buffered body is inflated in one step, which further amplifies memory use (CWE-409).
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
Allocation of Resources Without Limits or Throttling vulnerability in hackney_conn in benoitc hackney allows a malicious HTTP server to exhaust client memory via an oversized or highly compressed response body. hackney:request/5 and hackney:body/1 return the whole response body, and nothing bounds how much the connection process buffers. Any server the client requests can trigger it. hackney_conn:read_full_body/2 and the HTTP/2 and HTTP/3 accumulators append every chunk until the body ends. With {auto_decompress, true} the buffered body is then inflated in one step with zlib:gunzip/1 or zlib:inflate/2, which return the whole output at once. This issue affects hackney: from 2.0.0-beta.1 before 4.9.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- 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
Remediation
Upgrade hackney to version 4.9.0 or later.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA hackney (benoitc) Fixed in 4.9.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Advisory ·
benoitc hackney — hackney 4.9.0 release notes
5 records Highest priority Priority MEDIUM 2 MEDIUM, 3 LOW
Other records, highest priority first
- TI-2026-80383 Custom CA pinning bypass in hackney accepts public root certificatesPriority MEDIUM 41
- TI-2026-80384 SSRF allowlist bypass via encoded IPv6 literal in hackneyPriority LOW 29
- TI-2026-80370 hackney resends credentials on same-host redirects to another scheme or portPriority LOW 27
Timeline
- 2026-10-26 Threatist record created from CVE-2026-97200
- 2026-10-26 CISA SSVC decision points changed
- 2026-10-26 Priority changed: MEDIUM → LOW
- 2026-10-27 Alias added: GHSA-wpmp-4grc-56ph
- 2026-10-27 Priority changed: LOW → MEDIUM
References
More benoitc vulnerabilities
- 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-2026-34668 Infinite loop in Alt-Svc header parser 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-2024-06330 HTTP Request Smuggling in benoitc/gunicorn CVSS 3.0HIGH 7.5
Sources
- CVE-2026-97200 · CVE Program
- CVE-2026-97200 · NVD
- FIRST EPSS
- GHSA-wpmp-4grc-56ph · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences