FKIE_CVE-2026-85751

Vulnerability from fkie_nvd - Published: 2026-09-21 16:17 - Updated: 2026-09-21 18:17
Severity
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
Mailu is a mail server distributed as a set of Docker images. From Mailu 2.0 until 2024.06.55 and prior to Mailu helm-charts 2.7.3, deployments with PROXY_AUTH_WHITELIST configured but REAL_IP_HEADER unset trusted a client-controlled X-Forwarded-By header for header-based proxy authentication. The proxy_hide_header directive in the nginx template at core/nginx/conf/proxy.conf hid the header from upstream responses but did not overwrite the incoming request value in this configuration. An unauthenticated remote attacker could therefore spoof the trusted proxy identity and bypass authentication. This issue is fixed in Mailu 2024.06.55 and Mailu helm-charts 2.7.3.
References
security-advisories@github.comhttps://github.com/Mailu/Mailu/commit/dffa97cbd889ab208246372ce9c86e99abb27ae9
security-advisories@github.comhttps://github.com/Mailu/Mailu/commit/ff4003d045753013470945336448dbd790cac778
security-advisories@github.comhttps://github.com/Mailu/Mailu/pull/4070
security-advisories@github.comhttps://github.com/Mailu/Mailu/pull/4071
security-advisories@github.comhttps://github.com/Mailu/Mailu/releases/tag/2024.06.55
security-advisories@github.comhttps://github.com/Mailu/Mailu/security/advisories/GHSA-rfhj-4wcq-74xg
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "Mailu",
          "vendor": "Mailu",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.0.0, \u003c 2024.06.55"
            }
          ]
        },
        {
          "product": "helm-charts",
          "vendor": "Mailu",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.7.3"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mailu is a mail server distributed as a set of Docker images. From Mailu 2.0 until 2024.06.55 and prior to Mailu helm-charts 2.7.3, deployments with PROXY_AUTH_WHITELIST configured but REAL_IP_HEADER unset trusted a client-controlled X-Forwarded-By header for header-based proxy authentication. The proxy_hide_header directive in the nginx template at core/nginx/conf/proxy.conf hid the header from upstream responses but did not overwrite the incoming request value in this configuration. An unauthenticated remote attacker could therefore spoof the trusted proxy identity and bypass authentication. This issue is fixed in Mailu 2024.06.55 and Mailu helm-charts 2.7.3."
    }
  ],
  "id": "CVE-2026-85751",
  "lastModified": "2026-09-21T18:17:11.697",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-85751",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-21T17:56:04.999383Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-21T16:17:25.070",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Mailu/Mailu/commit/dffa97cbd889ab208246372ce9c86e99abb27ae9"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Mailu/Mailu/commit/ff4003d045753013470945336448dbd790cac778"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Mailu/Mailu/pull/4070"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Mailu/Mailu/pull/4071"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Mailu/Mailu/releases/tag/2024.06.55"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Mailu/Mailu/security/advisories/GHSA-rfhj-4wcq-74xg"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-290"
        },
        {
          "lang": "en",
          "value": "CWE-807"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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