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.

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Mon, 08 Jun 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 08 Jun 2026 14:30:00 +0000

Type Values Removed Values Added
Description 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.
Title gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection
First Time appeared Ninenines
Ninenines gun
Weaknesses CWE-346
CPEs cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*
Vendors & Products Ninenines
Ninenines gun
References
Metrics cvssV4_0

{'score': 6.3, 'vector': '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'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-06-08T16:34:45.350Z

Reserved: 2026-05-04T18:23:25.574Z

Link: CVE-2026-43972

cve-icon Vulnrichment

Updated: 2026-06-08T15:43:02.790Z

cve-icon NVD

Status : Received

Published: 2026-06-08T15:16:46.290

Modified: 2026-06-08T15:16:46.290

Link: CVE-2026-43972

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-08T15:30:27Z

Weaknesses