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CVE-2021-33624

Status: ModifiedMedium (4.7)—💥 PoC

In kernel/bpf/verifier.c in the Linux kernel before 5.12.13, a branch can be mispredicted (e.g., because of type confusion) and consequently an unprivileged BPF program can read arbitrary memory locations via a side-channel attack, aka CID-9183671af6db.

CVSS

Exploitation probability (EPSS)

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 (2)

Debian — Debian LinuxLinux — Linux Kernel

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-33624",
  "cveTags": [],
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          "version": "2.0.3",
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          "vectorString": "AV:L/AC:M/Au:N/C:C/I:N/A:N",
          "authentication": "NONE",
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        "obtainAllPrivilege": false,
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        "obtainUserPrivilege": false,
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    "cvssMetricV31": [
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          "value": "CWE-843"
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  "descriptions": [
    {
      "lang": "en",
      "value": "In kernel/bpf/verifier.c in the Linux kernel before 5.12.13, a branch can be mispredicted (e.g., because of type confusion) and consequently an unprivileged BPF program can read arbitrary memory locations via a side-channel attack, aka CID-9183671af6db."
    },
    {
      "lang": "es",
      "value": "En el archivo kernel/bpf/verifier.c en el kernel de Linux versiones anteriores a 5.12.13, una rama puede ser mal predicha (por ejemplo, debido a la confusión de tipos) y, en consecuencia, un programa BPF no privilegiado puede leer ubicaciones de memoria arbitrarias por medio de un ataque de canal lateral, también conocido como CID-9183671af6db"
    }
  ],
  "lastModified": "2026-10-08T21:17:35.550",
  "configurations": [
    {
      "nodes": [
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              "versionEndExcluding": "5.12.13"
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}