{"id":"CVE-2026-43972","state":"PUBLISHED","title":"gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection","description":"Origin Validation Error vulnerability in ninenines gun (gun_http2 module) allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE authority.\n\nIn 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.\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.","publishedAt":"2026-06-08T14:12:38.780Z","updatedAt":"2026-06-08T16:34:45.350Z","severity":{"score":6.3,"label":"Medium","version":"4.0","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","source":"EEF"},"assigner":"EEF","products":["ninenines gun"],"affected":[{"vendor":"ninenines","product":"gun","packageName":"gun","packageURL":"pkg:hex/gun","defaultStatus":"unaffected","versions":[{"version":"2.0.0","status":"affected","lessThan":"2.4.0","versionType":"semver"}],"cpes":["cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*"],"modules":["gun_http2"],"programFiles":["src/gun_http2.erl"],"programRoutines":[{"name":"gun_http2:push_promise_frame/7"},{"name":"gun_http2:headers_frame/9"}],"repo":"https://github.com/ninenines/gun"},{"vendor":"ninenines","product":"gun","packageName":"ninenines/gun","packageURL":"pkg:github/ninenines/gun","defaultStatus":"unaffected","versions":[{"version":"871989eef53663285c165fdfb83a5918ebe00d41","status":"affected","lessThan":"567863ff53802fed21c3b3f25812db7f7ae29676","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*"],"modules":["gun_http2"],"programFiles":["src/gun_http2.erl"],"programRoutines":[{"name":"gun_http2:push_promise_frame/7"},{"name":"gun_http2:headers_frame/9"}],"repo":"https://github.com/ninenines/gun.git"}],"references":["https://cna.erlef.org/cves/CVE-2026-43972.html","https://osv.dev/vulnerability/EEF-CVE-2026-43972","https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676"],"weaknesses":["CWE-346"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43972.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43972","state":"PUBLISHED","datePublished":"2026-06-08T14:12:38.780Z","dateUpdated":"2026-06-08T16:34:45.350Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-05-04T18:23:25.574Z"},"containers":{"cna":{"title":"gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection","descriptions":[{"lang":"en","value":"Origin Validation Error vulnerability in ninenines gun (gun_http2 module) allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE authority.\n\nIn 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.\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."}],"affected":[{"vendor":"ninenines","product":"gun","packageName":"gun","packageURL":"pkg:hex/gun","defaultStatus":"unaffected","versions":[{"version":"2.0.0","status":"affected","lessThan":"2.4.0","versionType":"semver"}],"cpes":["cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*"],"modules":["gun_http2"],"programFiles":["src/gun_http2.erl"],"programRoutines":[{"name":"gun_http2:push_promise_frame/7"},{"name":"gun_http2:headers_frame/9"}],"repo":"https://github.com/ninenines/gun"},{"vendor":"ninenines","product":"gun","packageName":"ninenines/gun","packageURL":"pkg:github/ninenines/gun","defaultStatus":"unaffected","versions":[{"version":"871989eef53663285c165fdfb83a5918ebe00d41","status":"affected","lessThan":"567863ff53802fed21c3b3f25812db7f7ae29676","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*"],"modules":["gun_http2"],"programFiles":["src/gun_http2.erl"],"programRoutines":[{"name":"gun_http2:push_promise_frame/7"},{"name":"gun_http2:headers_frame/9"}],"repo":"https://github.com/ninenines/gun.git"}],"references":[{"url":"https://cna.erlef.org/cves/CVE-2026-43972.html","tags":["related","third-party-advisory"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-43972","tags":["related"]},{"url":"https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676","tags":["patch"]}],"metrics":[{"cvssV4_0":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":6.3,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","userInteraction":"NONE","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-346","description":"CWE-346 Origin Validation Error","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-06-08T16:34:45.350Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>The vulnerability is exploitable only when gun is configured with a <tt>cookie_store</tt> and connects to an HTTP/2 server with server push enabled.</p>"}],"value":"The vulnerability is exploitable only when gun is configured with a cookie_store and connects to an HTTP/2 server with server push enabled."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:ninenines:gun:*:*:*:*:*:*:*:*","versionEndExcluding":"2.4.0","versionStartIncluding":"2.0.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Peter Ullrich"},{"lang":"en","type":"remediation developer","value":"Loïc Hoguin"}],"impacts":[{"capecId":"CAPEC-61","descriptions":[{"lang":"en","value":"CAPEC-61 Session Fixation"}]}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-06-08T15:42:59.352280Z","id":"CVE-2026-43972","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-06-08T15:43:06.577Z"}}]}}}