PT-2026-47298 · Ninenines · Gun

Loïc Hoguin + 1 · Published 2026-06-08 · Updated 2026-06-08 · CVE-2026-43972

NVD

CVSS v4.0

6.3

Medium

Base vector

AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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.

Fix

Origin Validation Error

Weakness Enumeration

CWE-346

Related Identifiers

CVE-2026-43972

Affected Products

Gun

References · 4

• https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-43972 · Security Note
• https://cna.erlef.org/cves/CVE-2026-43972.html · Note
• https://osv.dev/vulnerability/EEF-CVE-2026-43972 · Note