CVE-2026-115700 SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-115700?
CVE-2026-115700 is a medium-severity vulnerability in benoitc hackney, published on 26 Oct 2026.
Official 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.
Which versions are affected by CVE-2026-115700?
1 open source package ship an affected version, including hackney.
| Package | Affected | Fixed in |
|---|---|---|
hackney Hex | From 4.0.1 | 4.9.0 |
How do I fix CVE-2026-115700?
Upgrade hackney to 4.9.0 or later.
Is CVE-2026-115700 being exploited?
There is no known exploitation of CVE-2026-115700 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-115700, GHSA-8c7g-m8h7-q24x.