Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

CVE-2026-43966

Gravedad CVSS v4.0:
MEDIA
Tipo:
CWE-113 Neutralización incorrecta de secuencias CRLF en cabeceras HTTP (División de respuesta HTTP)
Fecha de publicación:
08/06/2026
Última modificación:
08/06/2026

Descripción

*** Pendiente de traducción *** Improper Neutralization of CRLF Sequences in HTTP Headers (&amp;#39;HTTP Request/Response Splitting&amp;#39;) vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.<br /> <br /> 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.<br /> <br /> This issue affects cowlib from 2.9.0.