CVE-2026-43972
MediumCVSS 6.3Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
The Origin Validation Error vulnerability in the gun_http2 module allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE headers. The :authority pseudo-header is stored verbatim without validation, violating protocol standards.
Risk Assessment
A malicious HTTP/2 server can plant cookies into the client's shared cookie store, leading to session fixation attacks and potential account takeover. No user interaction beyond making a normal HTTP/2 request to the attacker-controlled server is required.
Recommendation
It is recommended to upgrade to gun version 2.4.0 or later to mitigate this vulnerability. Additionally, monitor and validate the sources of HTTP/2 servers being connected to.
Original NVD description (English source)
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.