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CVE-2026-84501

Estado: AnalizadaMedia (5.3)—

An unauthenticated attacker can inject arbitrary fake log lines into Apache ZooKeeper's operational log by sending a crafted add_auth("ensemble", ...) request containing newline characters (\n). When the ensemble name doesn't match, EnsembleAuthenticationProvider.handleAuthentication() logs the raw, unsanitized name via LOG.warn(). Because SLF4J's {} placeholder preserves embedded newlines, the attacker can forge complete log entries — with arbitrary timestamps, log levels, class names, and messages — that are visually indistinguishable from genuine ZooKeeper log output.

This issue affects Apache ZooKeeper: from 3.9.0 through 3.9.5, from 3.8.0 through 3.8.6.

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Users are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.

CVSS

Probabilidad de explotación (EPSS)

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).

Tecnologías afectadas (1)

Apache — Zookeeper

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-84501",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-84501",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
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          ],
          "version": "2.0.3",
          "timestamp": "2026-09-16T19:42:27.138755Z"
        }
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    "cvssMetricV31": [
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
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        "exploitabilityScore": 3.9
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  "affected": [
    {
      "source": "security@apache.org",
      "affectedData": [
        {
          "vendor": "Apache Software Foundation",
          "product": "Apache ZooKeeper",
          "versions": [
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              "status": "affected",
              "version": "3.9.0",
              "versionType": "maven",
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  "published": "2026-09-16T10:16:53.557",
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      "tags": [
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  "weaknesses": [
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      "source": "security@apache.org",
      "description": [
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          "value": "CWE-117"
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  "descriptions": [
    {
      "lang": "en",
      "value": "An unauthenticated attacker can inject arbitrary fake log lines into Apache ZooKeeper's operational log by sending a crafted add_auth(\"ensemble\", ...) request containing newline characters (\\n). When the ensemble name doesn't match, EnsembleAuthenticationProvider.handleAuthentication() logs the raw, unsanitized name via LOG.warn(). Because SLF4J's {} placeholder preserves embedded newlines, the attacker can forge complete log entries — with arbitrary timestamps, log levels, class names, and messages — that are visually indistinguishable from genuine ZooKeeper log output.\n\nThis issue affects Apache ZooKeeper: from 3.9.0 through 3.9.5, from 3.8.0 through 3.8.6.\n\nUsers are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue."
    }
  ],
  "lastModified": "2026-09-18T14:36:51.747",
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