{"id":"EEF-CVE-2026-112880","summary":"CRLF injection in Proxy-Authorization header built from proxy_auth_fun in hackney","details":"## Summary\n\nImproper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in `hackney_http_connect` in benoitc hackney allows HTTP Request Splitting via the value a `proxy_auth_fun` callback returns. After a 407 response from an HTTP CONNECT proxy, `hackney_http_connect:handle_proxy_auth/11` calls the caller's `proxy_auth_fun` with the status code and the response headers and writes the returned binary into the `Proxy-Authorization` line of the CONNECT retry without checking it. A CR, LF or NUL byte in that value adds header lines to the request sent to the proxy.\n\nThe value is attacker-influenced when the callback derives it from untrusted data, for example from the proxy's challenge headers. Other caller-supplied values on the CONNECT path, such as the target host and the request headers, were already checked for control bytes.\n\nThis issue affects hackney: from 2.0.0 before 4.9.0.\n\n## Details\n\n**1. Challenge.** `hackney_http_connect:do_handshake_with_auth/9` in `src/hackney_http_connect.erl` sends the CONNECT request to the proxy. When the proxy answers 407 and the `proxy_auth_fun` option is set, it hands the status code and the parsed response headers to `hackney_http_connect:handle_proxy_auth/11`.\n\n**2. Callback result.** `handle_proxy_auth/11` calls the caller's `proxy_auth_fun` with those two values. On `{ok, AuthHeader}` it removes any existing `Proxy-Authorization` header and appends the binary `\u003c\u003c\"Proxy-Authorization: \", AuthHeader/binary\u003e\u003e` to the header list, then retries the handshake with it.\n\n**3. Splitting.** The header list is joined with CRLF into the CONNECT request. A CR, LF or NUL byte inside `AuthHeader` therefore ends the `Proxy-Authorization` line early and the rest is sent as further header lines. The target host and the request headers go through control-byte checks on this path; the callback result did not. The fix applies the same `has_ctl_bytes/1` check to it and returns `{error, {proxy_auth_error, invalid_header}}`.\n\n## Impact\n\nA party who controls what the application's `proxy_auth_fun` returns, for instance through the challenge headers of a proxy it can influence, can add header lines to the CONNECT request the client sends to its proxy.\n\n## Workarounds\n\nCheck the value your `proxy_auth_fun` is about to return for CR, LF and NUL bytes and return `{error, Reason}` instead when one is present. The callback runs in the application, so the check can be made there.\n\n## Configurations\n\nThe client connects through an HTTP CONNECT proxy with the `proxy_auth_fun` option set, and the callback builds its result from data an untrusted party can influence, such as the proxy's 407 challenge headers. Deployments without `proxy_auth_fun`, or whose callback returns a fixed credential, are not affected.","aliases":["CVE-2026-112880"],"modified":"2026-10-26T14:00:04.842750062Z","published":"2026-10-26T13:48:46.589Z","database_specific":{"cwe_ids":["CWE-113"],"capec_ids":["CAPEC-105"],"cpe_ids":["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://github.com/benoitc/hackney/releases/tag/4.9.0"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-112880.html"},{"type":"WEB","url":"https://github.com/benoitc/hackney/pull/989"},{"type":"WEB","url":"https://github.com/benoitc/hackney/commit/5df5a74a2817d5b12880d217db33253ff1fae1b5"},{"type":"FIX","url":"https://github.com/benoitc/hackney/commit/5ee7d7d19eba27e774667d472feb1e93a08af7f9"},{"type":"PACKAGE","url":"https://hex.pm/packages/hackney"}],"affected":[{"package":{"name":"hackney","ecosystem":"Hex","purl":"pkg:hex/hackney"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.0.0"},{"fixed":"4.9.0"}]}],"versions":["2.0.0","2.0.1","3.0.0","3.0.1","3.0.2","3.0.3","3.1.0","3.1.1","3.1.2","3.2.0","3.2.1","4.0.0","4.0.1","4.0.2","4.0.3","4.1.0","4.2.0","4.2.1","4.2.2","4.2.3","4.3.0","4.4.0","4.4.1","4.4.2","4.4.3","4.4.5","4.5.0","4.5.1","4.5.2","4.6.0","4.6.1","4.7.0","4.7.1","4.7.2","4.7.3","4.7.4","4.8.0","4.8.1","4.8.2","4.8.3","4.8.4","4.8.5","4.8.6","4.8.7"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-112880.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/benoitc/hackney","events":[{"introduced":"5df5a74a2817d5b12880d217db33253ff1fae1b5"},{"fixed":"5ee7d7d19eba27e774667d472feb1e93a08af7f9"}]}],"versions":["4.8.7","4.8.6","4.8.5","4.8.4","4.8.3","4.8.2","4.8.1","4.8.0","4.7.4","4.7.3","4.7.2","4.7.1","4.7.0","4.6.1","4.6.0","4.5.2","4.5.1","4.5.0","4.4.5","4.4.4","4.4.3","4.4.2","4.4.1","4.4.0","4.3.0","4.2.3","4.2.2","4.2.1","4.2.0","4.1.0","4.0.3","4.0.2","4.0.1","4.0.0","3.2.1","3.2.0","3.1.2","3.1.1","3.1.0","3.0.3","3.0.2","3.0.1","2.0.1","2.0.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-112880.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N"}],"credits":[{"name":"Daniel Coles","type":"FINDER"},{"name":"Daniel Coles","type":"REPORTER"},{"name":"Benoit Chesneau","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}