{"id":"CVE-2026-64785","aliases":["GHSA-q3g2-m552-3r9c"],"url":"https://o3.security/vulnerability/CVE-2026-64785","summary":"swift-nio-http2: Missing CR/LF/NUL validation in header values","details":"## Summary\n\nSwiftNIO HTTP/2 was missing validation on inbound HEADERS frames that let\nCR, LF, NUL, SP and other control characters reach an HTTP/1.1 backend\nthrough NIOHTTP2's HTTP/2-to-HTTP/1 codec, enabling HTTP request smuggling\nor response splitting.\n\n## Impact\n\nTwo related gaps in inbound header validation, against any application\nusing HTTP2ToHTTP1Codec (or HTTP2FramePayloadToHTTP1Codec) to front an\nHTTP/1.1 backend:\n\nRegular header field values were only checked against a forbidden-name\nlist (connection, transfer-encoding, proxy-connection, keep-alive,\nupgrade); the value itself was never inspected. An attacker-controlled\nregular header field value containing CR or LF passed validation and, once\nserialized as `name: value CRLF` by the codec, terminated the field early\nand injected extra header lines into the outbound HTTP/1.1 message.\n\nPseudo-header values (`:path` in particular) were only checked against\nCR, LF and NUL. A `:path` value containing SP serializes into the\nrequest-target of `METHOD SP request-target SP HTTP-version CRLF`, so a\nvalue like `/a HTTP/1.1` produces `GET /a HTTP/1.1 HTTP/1.1` — a\nparser-differential request line depending on whether a downstream reader\ntakes the first or last SP-delimited token as the version.\n\nNeither of these is reachable on a stock pipeline: NIOHTTP1's outbound\nvalidator (`enableOutboundHeaderValidation`, on by default) already rejects\nthese characters on write. The exposure is pipelines that skip outbound\nvalidation, or any code that reads validated-looking `HTTPRequestHead.headers`\nand forwards the values on trusting that HTTP/2 already checked them.\n\n## Fix\n\nFixed in 48bfd90 and 45bdf67.\n\n## Mitigation\n\nUpgrade to 1.45.0","published":"2026-07-23T20:17:21.440Z","modified":"2026-10-20T12:02:10.915035943Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"epss":{"score":0.00181,"percentile":0.07838,"asOf":"2026-09-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"SwiftURL","name":"swift-nio-http2","fixedVersion":"1.45.0"}],"fix":{"url":"https://github.com/apple/swift-nio-http2/commit/45bdf670248be5f16ec0340e125dca285536f0fb","label":"apple/swift-nio-http2@45bdf67"},"references":[{"type":"FIX","url":"https://github.com/apple/swift-nio-http2/security/advisories/GHSA-q3g2-m552-3r9c"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64785"},{"type":"WEB","url":"https://github.com/apple/swift-nio-http2/commit/45bdf670248be5f16ec0340e125dca285536f0fb"},{"type":"WEB","url":"https://github.com/apple/swift-nio-http2/commit/48bfd9067d7d1d15c4789440127a0cf36222ea43"},{"type":"PACKAGE","url":"https://github.com/apple/swift-nio-http2"},{"type":"WEB","url":"https://github.com/apple/swift-nio-http2/releases/tag/1.45.0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T12:02:10.915035943Z"}}