Vulnerability · Published Oct 26, 2026 · Assigned by EEF
CVE-2026-115700SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney
Medium 6.9
In plain English
A medium-severity server-side request forgery in hackney from benoitc. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 3% of all known vulnerabilities).
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.
Affected products (as reported)
Weakness: CWE-436, CWE-918 · 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
References
- hackney 4.9.0 release notes vendor-advisory, related
- EEF CNA record for CVE-2026-115700 related
- OSV record EEF-CVE-2026-115700 related
- Refuse bracketed and trailing-dot IP literals in normalize/2 (benoitc/hackney#987) related
- Introducing commit 452620a in benoitc/hackney related
- Fix commit f19561a in benoitc/hackney patch