---
id: CVE-2026-115700
title: >-
  SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP
  literal in hackney
summary: >-
  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%…
severity: medium
cvss: 6.9
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-436
  - CWE-918
vendor: benoitc
product: hackney
affected:
  - hackney >= 4.0.1 < 4.9.0
  - >-
    benoitc/hackney >= 452620a92ec1da2e6b4862a049a2a4f04b42068f <
    f19561a0b422376348c91537e51377ab7325f4ee
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T13:49:02.744Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-115700'
references:
  - url: 'https://github.com/benoitc/hackney/releases/tag/4.9.0'
    label: hackney 4.9.0 release notes
  - url: 'https://cna.erlef.org/cves/CVE-2026-115700.html'
    label: EEF CNA record for CVE-2026-115700
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-115700'
    label: OSV record EEF-CVE-2026-115700
  - url: 'https://github.com/benoitc/hackney/pull/987'
    label: >-
      Refuse bracketed and trailing-dot IP literals in normalize/2
      (benoitc/hackney#987)
  - url: >-
      https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f
    label: Introducing commit 452620a in benoitc/hackney
  - url: >-
      https://github.com/benoitc/hackney/commit/f19561a0b422376348c91537e51377ab7325f4ee
    label: Fix commit f19561a in benoitc/hackney
tags:
  - cve.org
ingestedAt: '2026-10-26T14:27:31.814Z'
---

## Overview

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.

## Affected

- `hackney >= 4.0.1 < 4.9.0`
- `benoitc/hackney >= 452620a92ec1da2e6b4862a049a2a4f04b42068f < f19561a0b422376348c91537e51377ab7325f4ee`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### Workarounds

Run the allowlist on the host that hackney_url:normalize/1 returns for the parsed URL, and strip a surrounding bracket pair and a trailing dot from it before the IP check, so the check sees the same address the connect path uses.