Summary
Hackney: Cross-origin Redirect Leaks Authorization, Cookie, and Request Body
The HTTP/3 redirect handler in src/hackney_h3.erl forwards the original request headers (Authorization, Cookie, Proxy-Authorization) and, for 307/308 responses, the original request body to the redirect target without checking whether the target host matches the origin. When follow_redirect is enabled and a server responds with a cross-origin Location, hackney delivers the caller's credentials verbatim to the attacker-controlled host. The main hackney HTTP/1 client has maybe_strip_auth_on_redirect/2 (the fix for CVE-2018-1000007); the H3 client was added later without it.
Details
In src/hackney_h3.erl, handle_redirect/11 (line 165) extracts the redirect target from the server-controlled Location header via get_redirect_location/1 and resolves it with resolve_redirect_url/2, which accepts any absolute http:// or https:// URL. It then calls do_request_with_redirect/8 passing the original Headers list unchanged. For 307/308 responses, redirect_method/2 preserves the original method and body, so the POST body is also forwarded.
No comparison is made between the original URL's scheme, host, or port and the redirect target. The downstream connect/3 opens a new QUIC connection to whatever the Location header named, and build_request_headers/4 serializes the unmodified headers into the QPACK-encoded request.
PoC
- Issue an HTTP/3 POST to an attacker-controlled origin with
follow_redirect => trueand anAuthorization: Bearer ...header. - The attacker's server responds
307 Location: https://other.host/collect. - hackney opens a new connection to
other.hostand re-sends the original headers and body, including the bearer token and anyCookieheaders.
Resources
Impact
Credential and request-body disclosure to attacker-controlled origins. Affects hackney 3.1.1 through 4.0.0 when using the HTTP/3 client with follow_redirect enabled. Any upstream that is malicious, compromised, or reachable via DNS/MITM can steal session tokens, bearer credentials, and POST bodies. CVSS v4.0: 6.0 (MEDIUM).
Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-47070? CVE-2026-47070 is a medium-severity open redirect vulnerability in hackney (erlang), affecting versions >= 3.1.1, < 4.0.1. It is fixed in 4.0.1. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
- Which versions of hackney are affected by CVE-2026-47070? hackney (erlang) versions >= 3.1.1, < 4.0.1 is affected.
- Is there a fix for CVE-2026-47070? Yes. CVE-2026-47070 is fixed in 4.0.1. Upgrade to this version or later.
- Is CVE-2026-47070 exploitable, and should I be worried? Whether CVE-2026-47070 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-47070 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-47070? Upgrade
hackneyto 4.0.1 or later.