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CVE-2026-43972— gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection

Quick assessment

Affected
ninenines gun
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Gun是Nine Nines开源的一款支持HTTP/1.1、HTTP/2和WebSocket的Erlang HTTP客户端。 gun 2.0.0版本至2.4.0之前版本存在访问控制错误漏洞，该漏洞源于gun_http2模块存在源验证错误，可能导致跨源Cookie注入，允许恶意或受损的HTTP/2服务器在客户端共享Cookie存储中植入任意第三方域的Cookie。

AI Predicted 8.1 Difficulty: Easy EPSS 0.20% · P9

Affected Version Matrix 2

VendorProduct Version RangeStatus
ninenines gun 2.0.0< 2.4.0 affected
871989eef53663285c165fdfb83a5918ebe00d41< 567863ff53802fed21c3b3f25812db7f7ae29676 affected
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I. Basic Information for CVE-2026-43972

Vulnerability Information
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Vulnerability Title
gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
源验证错误
Source: CVE Program / CVE List V5
Vulnerability Title
Gun 访问控制错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Gun是Nine Nines开源的一款支持HTTP/1.1、HTTP/2和WebSocket的Erlang HTTP客户端。 gun 2.0.0版本至2.4.0之前版本存在访问控制错误漏洞，该漏洞源于gun_http2模块存在源验证错误，可能导致跨源Cookie注入，允许恶意或受损的HTTP/2服务器在客户端共享Cookie存储中植入任意第三方域的Cookie。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ninenines gun 2.0.0 ~ 2.4.0 cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*
ninenines gun 871989eef53663285c165fdfb83a5918ebe00d41 ~ 567863ff53802fed21c3b3f25812db7f7ae29676 cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-43972

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III. Intelligence Information for CVE-2026-43972

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Patches & Fixes for CVE-2026-43972 (1)

Vendor Advisories for CVE-2026-43972 (2)

Same Patch Batch · ninenines · 2026-06-08 · 4 CVEs total

CVE-2026-43973 gun HTTP/1.1 response buffer has no size limit allowing server-controlled memory exhaustio
CVE-2026-43966 HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2
CVE-2026-43974 gun HTTP/1.1 client accepts unsolicited 101 Switching Protocols response allowing server-d

IV. Related Vulnerabilities

Same product: gun
Same vendor: ninenines
Same weakness: CWE-346

V. Comments for CVE-2026-43972

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