{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-27959","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-02-25T03:24:57.792Z","datePublished":"2026-02-26T01:45:45.668Z","dateUpdated":"2026-02-26T19:32:00.105Z"},"containers":{"cna":{"title":"Koa has Host Header Injection via `ctx.hostname`","problemTypes":[{"descriptions":[{"cweId":"CWE-20","lang":"en","description":"CWE-20: Improper Input Validation","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","version":"3.1"}}],"references":[{"name":"https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm","tags":["x_refsource_CONFIRM"],"url":"https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm"},{"name":"https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df","tags":["x_refsource_MISC"],"url":"https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df"},{"name":"https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb","tags":["x_refsource_MISC"],"url":"https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb"}],"affected":[{"vendor":"koajs","product":"koa","versions":[{"version":">= 3.0.0, < 3.1.2","status":"affected"},{"version":"< 2.16.4","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-02-26T01:45:45.668Z"},"descriptions":[{"lang":"en","value":"Koa is middleware for Node.js using ES2017 async functions. Prior to versions 3.1.2 and 2.16.4, Koa's `ctx.hostname` API performs naive parsing of the HTTP Host header, extracting everything before the first colon without validating the input conforms to RFC 3986 hostname syntax. When a malformed Host header containing a `@` symbol is received, `ctx.hostname` returns `evil[.]com` - an attacker-controlled value. Applications using `ctx.hostname` for URL generation, password reset links, email verification URLs, or routing decisions are vulnerable to Host header injection attacks. Versions 3.1.2 and 2.16.4 fix the issue."}],"source":{"advisory":"GHSA-7gcc-r8m5-44qm","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-02-26T19:31:17.215940Z","id":"CVE-2026-27959","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-02-26T19:32:00.105Z"}}]}}