CVE-2026-115700
SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney
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.
Fixes and workarounds
Workaround
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.
Source: CNA: EEFFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: EEFAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| hackney benoitc hackney
hex |
≥ 4.0.1; < 4.9.0 (affected, semver)
Other versions: unaffected |
CNA: EEF |
| hackney benoitc benoitc/hackney
github |
≥ 452620a92ec1da2e6b4862a049a2a4f04b42068f; < f19561a0b422376348c91537e51377ab7325f4ee (affected, git)
Other versions: unaffected |
CNA: EEF |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 6.9 medium |
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 | CNA: EEF |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/benoitc/hackney/releases/tag/4.9.0CNA: EEF · vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-115700.htmlCNA: EEF · related
- https://osv.dev/vulnerability/EEF-CVE-2026-115700CNA: EEF · related
- https://github.com/benoitc/hackney/pull/987CNA: EEF · related
- https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068fCNA: EEF · related
- https://github.com/benoitc/hackney/commit/f19561a0b422376348c91537e51377ab7325f4eeCNA: EEF · patch
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