CVE-2026-43972

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.

CVSS

No CVSS.

References

Link	Resource
https://cna.erlef.org/cves/CVE-2026-43972.html
https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676
https://osv.dev/vulnerability/EEF-CVE-2026-43972

Configurations

No configuration.

History

08 Jun 2026, 15:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-08 15:16

Updated : 2026-06-17 10:50

NVD link : CVE-2026-43972

Mitre link : CVE-2026-43972

CVE.ORG link : CVE-2026-43972

JSON object : View

Products Affected

No product.

CWE

CWE-346

Origin Validation Error

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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 \u00a710.6 / RFC 9113 \u00a78.4, which require receivers to treat as a protocol error any push for a resource the server is not authoritative for.\n\nA 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.\n\nThis issue affects gun: from 2.0.0 before 2.4.0."}], "lastModified": "2026-06-17T10:50:08.800", "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}