{"id":"DEBIAN-CVE-2026-43966","details":"Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.  cow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20–0x7E, excluding \" and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.  This issue affects cowlib from 2.9.0.","modified":"2026-09-26T12:00:08.384834280Z","published":"2026-06-08T17:16:43.447Z","upstream":["CVE-2026-43966"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-43966"}],"affected":[{"package":{"name":"erlang-cowboy","ecosystem":"Debian:14","purl":"pkg:deb/debian/erlang-cowboy?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.16.1+dfsg-1"}]}],"versions":["0.10.0+dfsg1-1","0.6.1-1","0.6.1-2","0.6.1-3","0.6.1-4","0.8.6+dfsg-1","0.8.6+dfsg1-1","1.0.0+dfsg1-1","2.0.0~pre.1+dfsg1-1","2.0.0~pre.1+dfsg1-2","2.0.0~pre.1+dfsg1-3","2.0.0~pre.1+dfsg1-4"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-43966.json"}},{"package":{"name":"rabbitmq-server","ecosystem":"Debian:12","purl":"pkg:deb/debian/rabbitmq-server?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.10.8-1.1","3.10.8-1.1+deb12u1","3.10.8-2","3.10.8-3","3.10.8-4","3.12.1-1","3.12.1-1.1","4.0.5-1","4.0.5-10","4.0.5-11","4.0.5-12","4.0.5-13","4.0.5-14","4.0.5-2","4.0.5-3","4.0.5-4","4.0.5-5","4.0.5-6","4.0.5-8","4.0.5-9","4.3.0-1","4.3.0-2","4.3.0-3","4.3.2-1","4.3.2-2","4.3.2-3","4.3.2-4","4.3.2-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-43966.json"}},{"package":{"name":"rabbitmq-server","ecosystem":"Debian:13","purl":"pkg:deb/debian/rabbitmq-server?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.0.5-10","4.0.5-11","4.0.5-12","4.0.5-13","4.0.5-14","4.0.5-6","4.0.5-6+deb13u1","4.0.5-6+deb13u2","4.0.5-8","4.0.5-9","4.3.0-1","4.3.0-2","4.3.0-3","4.3.2-1","4.3.2-2","4.3.2-3","4.3.2-4","4.3.2-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-43966.json"}},{"package":{"name":"rabbitmq-server","ecosystem":"Debian:14","purl":"pkg:deb/debian/rabbitmq-server?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.0.5-10","4.0.5-11","4.0.5-12","4.0.5-13","4.0.5-14","4.0.5-6","4.0.5-8","4.0.5-9","4.3.0-1","4.3.0-2","4.3.0-3","4.3.2-1","4.3.2-2","4.3.2-3","4.3.2-4","4.3.2-5"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-43966.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}