CVE-2026-47070: HTTP/3 redirect handler leaks Authorization and Cookie headers to cross-origin redirect target in hackney
Summary
The HTTP/3 redirect handler in src/hackneyh3.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 followredirect 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 maybestripauthonredirect/2 (the fix for CVE-2018-1000007); the H3 client was added later without it.
Details
In src/hackneyh3.erl, handleredirect/11 (line 165) extracts the redirect target from the server-controlled Location header via getredirectlocation/1 and resolves it with resolveredirecturl/2, which accepts any absolute http:// or https:// URL. It then calls dorequestwithredirect/8 passing the original Headers list unchanged. For 307/308 responses, redirectmethod/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 buildrequestheaders/4 serializes the unmodified headers into the QPACK-encoded request.
PoC
1. Issue an HTTP/3 POST to an attacker-controlled origin with followredirect => true and an Authorization: Bearer ... header. 2. The attacker's server responds 307 Location: https://other.host/collect. 3. hackney opens a new connection to other.host and re-sends the original headers and body, including the bearer token and any Cookie headers.
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 followredirect 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).
Resources
Introduction commit: https://github.com/benoitc/hackney/commit/e61b7d04b7826847e1efe614106ef4d580c78eab Patch commit: https://github.com/benoitc/hackney/commit/c58d5b50bade146360b85caf3dc8065807b08246
Other sources
Sensitive Data Exposure vulnerability in benoitc hackney allows Retrieve Embedded Sensitive Data. The HTTP/3 redirect handler in src/hackneyh3.erl passes the original request headers unchanged to the redirect target without performing any cross-origin check. When a client issues an HTTP/3 request with followredirect enabled and includes Authorization or Cookie headers, a server responding with a 3xx redirect to a different host will cause the client to forward those credentials verbatim to the new origin.
The main hackney.erl module has maybestripauthonredirect/2 (guarded by the locationtrusted option) to address CVE-2018-1000007, but hackneyh3.erl is missing this protection entirely.
This issue affects hackney: from 3.1.1 before 4.0.1.
— NVD
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
erlang/hackneyto a version that resolves this vulnerability.Fixed in 4.0.1 - Upgrade
Upgrade
benoitc/hackneyto a version that resolves this vulnerability.Fixed in 4.0.1 - Configuration
When using hackney’s HTTP/3 client, do not use follow_redirect=true; set follow_redirect to false to prevent cross-origin redirects from forwarding Authorization/Cookie (and for 307/308, the original POST body) to attacker-controlled Location targets.
hackney HTTP/3 client (hackney_h3.erl) follow_redirect = false
Event History
Frequently Asked Questions
What is the severity of CVE-2026-47070?
CVE-2026-47070 has a risk score of 55.
What type of vulnerability is CVE-2026-47070?
CVE-2026-47070 is classified as a Sensitive Data Exposure vulnerability.
How does CVE-2026-47070 affect the hackney software?
CVE-2026-47070 allows the HTTP/3 redirect handler to leak Authorization and Cookie headers to cross-origin redirect targets.
How can I fix CVE-2026-47070?
To fix CVE-2026-47070, update your hackney library to a version that mitigates this vulnerability.
What should I do if I am impacted by CVE-2026-47070?
If impacted by CVE-2026-47070, immediately review your use of the hackney library and ensure appropriate headers are not being leaked during redirects.