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CVE-2026-23472

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: serial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN uart_write_room() and uart_write() behave inconsistently when xmit_buf is NULL (which happens for PORT_UNKNOWN ports that were never properly initialized): - uart_write_room() returns kfifo_avail() which can be > 0 - uart_write() checks xmit_buf and returns 0 if NULL This inconsistency causes an infinite loop in drivers that rely on tty_write_room() to determine if they can write: while (tty_write_room(tty) > 0) { written = tty->ops->write(...); // written is always 0, loop never exits } For example, caif_serial's handle_tx() enters an infinite loop when used with PORT_UNKNOWN serial ports, causing system hangs. Fix by making uart_write_room() also check xmit_buf and return 0 if it's NULL, consistent with uart_write(). Reproducer: https://gist.github.com/mrpre/d9a694cc0e19828ee3bc3b37983fde13

Severity
MEDIUM
CVSS score
5.5 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-04-03 16:16:34.977000
Last modified
2026-10-30 13:18:38.927000
View original CVE JSON 
{
  "id": "CVE-2026-23472",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-04-03T16:16:34.977",
  "lastModified": "2026-10-30T13:18:38.927",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nserial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN\n\nuart_write_room() and uart_write() behave inconsistently when\nxmit_buf is NULL (which happens for PORT_UNKNOWN ports that were\nnever properly initialized):\n\n- uart_write_room() returns kfifo_avail() which can be > 0\n- uart_write() checks xmit_buf and returns 0 if NULL\n\nThis inconsistency causes an infinite loop in drivers that rely on\ntty_write_room() to determine if they can write:\n\n  while (tty_write_room(tty) > 0) {\n      written = tty->ops->write(...);\n      // written is always 0, loop never exits\n  }\n\nFor example, caif_serial's handle_tx() enters an infinite loop when\nused with PORT_UNKNOWN serial ports, causing system hangs.\n\nFix by making uart_write_room() also check xmit_buf and return 0 if\nit's NULL, consistent with uart_write().\n\nReproducer: https://gist.github.com/mrpre/d9a694cc0e19828ee3bc3b37983fde13"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nserial: core: corrección de bucle infinito en handle_tx() para PORT_UNKNOWN\n\nuart_write_room() y uart_write() se comportan de forma inconsistente cuando xmit_buf es NULL (lo cual ocurre para puertos PORT_UNKNOWN que nunca fueron inicializados correctamente):\n\n- uart_write_room() devuelve kfifo_avail() que puede ser > 0\n- uart_write() comprueba xmit_buf y devuelve 0 si es NULL\n\nEsta inconsistencia causa un bucle infinito en controladores que dependen de tty_write_room() para determinar si pueden escribir:\n\n  while (tty_write_room(tty) > 0) {\n      written = tty->ops->write(...);\n      // written es siempre 0, el bucle nunca sale\n  }\n\nPor ejemplo, el handle_tx() de caif_serial entra en un bucle infinito cuando se usa con puertos serie PORT_UNKNOWN, causando cuelgues del sistema.\n\nSolución al hacer que uart_write_room() también compruebe xmit_buf y devuelva 0 si es NULL, consistente con uart_write().\n\nReproductor: https://gist.github.com/mrpre/d9a694cc0e19828ee3bc3b37983fde13"
    }
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          "product": "Linux",
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              "status": "unaffected"
            },
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              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
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            }
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  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
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          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6
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  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Primary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-835"
        }
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    }
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          "negate": false,
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