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CVE-2018-12633

Status: ModifiedMedium (6.3)—PoC
Severity6.3Medium · CVSS 3.0
Exploitation probability0.26 %higher than 17% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitAvailableProof of concept on GitHub (unverified)

An issue was discovered in the Linux kernel through 4.17.2. vbg_misc_device_ioctl() in drivers/virt/vboxguest/vboxguest_linux.c reads the same user data twice with copy_from_user. The header part of the user data is double-fetched, and a malicious user thread can tamper with the critical variables (hdr.size_in and hdr.size_out) in the header between the two fetches because of a race condition, leading to severe kernel errors, such as buffer over-accesses. This bug can cause a local denial of service and information leakage.

CVSS

Base score
6.3
Version
3.0
Vector
CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
0.26 %
Percentile among all scored CVEs
17
Score date
10/20/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Public exploits

Exploit code or detection templates are publicly available. This is not the same as confirmed active exploitation (KEV), but it raises the risk: patch with priority.

⚠️ GitHub proofs of concept are not verified: some are fake or contain malware. Never run them outside an isolated lab.

Affected technologies (1)

Linux — Linux Kernel

CWEs

References

Show 6 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2018-12633",
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          "vectorString": "AV:L/AC:M/Au:N/C:C/I:N/A:C",
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          "versions": [
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  "published": "2018-06-22T00:29:00.270",
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  "vulnStatus": "Modified",
  "weaknesses": [
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  "descriptions": [
    {
      "lang": "en",
      "value": "An issue was discovered in the Linux kernel through 4.17.2. vbg_misc_device_ioctl() in drivers/virt/vboxguest/vboxguest_linux.c reads the same user data twice with copy_from_user. The header part of the user data is double-fetched, and a malicious user thread can tamper with the critical variables (hdr.size_in and hdr.size_out) in the header between the two fetches because of a race condition, leading to severe kernel errors, such as buffer over-accesses. This bug can cause a local denial of service and information leakage."
    },
    {
      "lang": "es",
      "value": "Se ha descubierto un problema en el kernel de Linux hasta la versión 4.17.2. vbg_misc_device_ioctl() en drivers/virt/vboxguest/vboxguest_linux.c lee los mismos datos de usuario dos veces con copy_from_user. La cabecera de los datos de usuario es de tipo double-fetch y un hilo de usuario malicioso puede falsificar las variables críticas (hdr.size_in y hdr.size_out) en la cabecera entre los dos fetch debido a una condición de carrera. Esto desemboca en varios errores del kernel, como accesos específicos al búfer. Este error puede provocar una denegación de servicio (DoS) local y una fuga de información."
    }
  ],
  "lastModified": "2026-06-17T01:38:05.937",
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  "sourceIdentifier": "cve@mitre.org"
}