CVE-2026-23457

Estado: ModificadaAlta (8.6)—

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()

sip_help_tcp() parses the SIP Content-Length header with simple_strtoul(), which returns unsigned long, but stores the result in unsigned int clen. On 64-bit systems, values exceeding UINT_MAX are silently truncated before computing the SIP message boundary.

For example, Content-Length 4294967328 (2^32 + 32) is truncated to 32, causing the parser to miscalculate where the current message ends. The loop then treats trailing data in the TCP segment as a second SIP message and processes it through the SDP parser.

Leer descripción completaMostrar menos

Fix this by changing clen to unsigned long to match the return type of simple_strtoul(), and reject Content-Length values that exceed the remaining TCP payload length.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Puntuación base: 8.6

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.43%
Percentil entre todas las CVEs puntuadas: 36
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access85 %
Impacto principalT1499.004 Application or System Exploitationimpact75 %
Impacto secundarioT1565.002 Transmitted Data Manipulationimpact65 %

Vulnerabilidad en netfilter (AV:N, PR:N) permite truncación de Content-Length que causa parseo incorrecto de mensajes SIP, habilitando DoS (A:H) e inyección de datos (I:L) en sistemas Linux.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Filter Network Traffic Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Encrypt Sensitive Information

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

NVD-CWE-noinfo

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()\n\nsip_help_tcp() parses the SIP Content-Length header with\nsimple_strtoul(), which returns unsigned long, but stores the result in\nunsigned int clen.  On 64-bit systems, values exceeding UINT_MAX are\nsilently truncated before computing the SIP message boundary.\n\nFor example, Content-Length 4294967328 (2^32 + 32) is truncated to 32,\ncausing the parser to miscalculate where the current message ends.  The\nloop then treats trailing data in the TCP segment as a second SIP\nmessage and processes it through the SDP parser.\n\nFix this by changing clen to unsigned long to match the return type of\nsimple_strtoul(), and reject Content-Length values that exceed the\nremaining TCP payload length."
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      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnetfilter: nf_conntrack_sip: corrección de la truncación u32 de Content-Length en sip_help_tcp()\n\nsip_help_tcp() analiza la cabecera SIP Content-Length con simple_strtoul(), que devuelve unsigned long, pero almacena el resultado en unsigned int clen. En sistemas de 64 bits, los valores que exceden UINT_MAX se truncan silenciosamente antes de calcular el límite del mensaje SIP.\n\nPor ejemplo, Content-Length 4294967328 (2^32 + 32) se trunca a 32, provocando que el analizador calcule erróneamente dónde termina el mensaje actual. El bucle entonces trata los datos restantes en el segmento TCP como un segundo mensaje SIP y lo procesa a través del analizador SDP.\n\nSe corrige esto cambiando clen a unsigned long para que coincida con el tipo de retorno de simple_strtoul(), y rechazando los valores de Content-Length que exceden la longitud restante de la carga útil TCP."
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