Vulnerability advisory
EEF-CVE-2026-43972
gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection
Also known as CVE-2026-43972GHSA-36w4-95hv-5vwg
- CVSS 4.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
Affected versions
| Affected | Fixed in |
|---|---|
2.0.0 to before 2.4.0 | 2.4.0Advisories → |
Repository
| Affected commits | Fixed by commit |
|---|---|
| GIT github.com/ninenines/gun.git ↗ | |
| 871989eef53663285c165fdfb83a5918ebe00d41 to before 567863ff53802fed21c3b3f25812db7f7ae29676 | 567863ff53802fed21c3b3f25812db7f7ae29676 |
Also listed as affected (9)
| |
Description
Summary
Origin Validation Error vulnerability in ninenines gun (gun_http2 module) allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE authority.
In gun_http2:push_promise_frame/7, the :authority pseudo-header from an incoming PUSH_PROMISE frame is stored verbatim into the promised stream record without checking that it matches the connection's origin. When gun_http2:headers_frame/9 later processes the response headers for the promised stream, it calls gun_cookies:set_cookie_header/7 with the unvalidated server-supplied authority before any status branching and before user code can act. This violates RFC 7540 §10.6 / RFC 9113 §8.4, which require receivers to treat as a protocol error any push for a resource the server is not authoritative for.
A malicious or compromised HTTP/2 server can plant cookies scoped to arbitrary third-party domains into the client's shared cookie store. This enables session fixation attacks against those domains and, if the planted cookie overrides a legitimate session token, may result in account takeover. No user interaction beyond making a normal HTTP/2 request to the attacker-controlled server is required.
This issue affects gun: from 2.0.0 before 2.4.0.
Configurations
The vulnerability is exploitable only when gun is configured with a cookie_store and connects to an HTTP/2 server with server push enabled.