gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-346.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| ninenines | gun | 2.0.0 to before 2.4.0 | 2.4.0 | Patch available | CNA |
| — | gun (Hex) | 2.0.0 to before 2.4.0 | 2.4.0 | Patch available | GHSA-36w4-95hv-5vwg |
- gun Vendorninenines Affected 2.0.0 to before 2.4.0 Fixed in 2.4.0 Patch available CNA
- gun (Hex) Vendor— Affected 2.0.0 to before 2.4.0 Fixed in 2.4.0 Patch available GHSA-36w4-95hv-5vwg
Remediation
- Fix · CNA gun (ninenines) Fixed in 2.4.0
- Fix · GHSA-36w4-95hv-5vwg gun (Hex) Fixed in 2.4.0 Advisory →
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
ninenines gun 2.4.0
3 records Highest priority Priority MEDIUM 2 MEDIUM, 1 LOW
Other records, highest priority first
- TI-2026-32019 gun HTTP/1.1 client accepts unsolicited 101 Switching Protocols response allowing server-driven protocol hijack and OOMPriority MEDIUM 44
- TI-2026-32018 gun HTTP/1.1 response buffer has no size limit allowing server-controlled memory exhaustionPriority MEDIUM 44
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-43972
- 2026-10-03 Alias added: GHSA-36w4-95hv-5vwg
References
More ninenines Gun vulnerabilities
- TI-2026-32019 gun HTTP/1.1 client accepts unsolicited 101 Switching Protocols response allowing server-driven protocol hijack and OOM CVSS 4.0HIGH 8.7
- TI-2026-32018 gun HTTP/1.1 response buffer has no size limit allowing server-controlled memory exhaustion CVSS 4.0HIGH 8.7
Sources
- CVE-2026-43972 · CVE Program
- CVE-2026-43972 · NVD
- FIRST EPSS
- GHSA-36w4-95hv-5vwg · GitHub Advisory Database · CC BY 4.0
- CVE-2026-43972 · Red Hat security data · CC BY 4.0
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