CVE-2026-27588 (GCVE-0-2026-27588)

Vulnerability from cvelistv5 – Published: 2026-02-24 16:28 – Updated: 2026-02-24 16:28
VLAI?
Title
Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass
Summary
Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (>100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue.
Severity ?
7.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
CWE
  • CWE-178 - Improper Handling of Case Sensitivity
Assigner
References
Impacted products
Vendor Product Version
caddyserver caddy Affected: < 2.11.1
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          "vendor": "caddyserver",
          "versions": [
            {
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        }
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            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-178",
              "description": "CWE-178: Improper Handling of Case Sensitivity",
              "lang": "en",
              "type": "CWE"
            }
          ]
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      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-24T16:28:28.106Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8"
        },
        {
          "name": "https://github.com/caddyserver/caddy/releases/tag/v2.11.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/caddyserver/caddy/releases/tag/v2.11.1"
        }
      ],
      "source": {
        "advisory": "GHSA-x76f-jf84-rqj8",
        "discovery": "UNKNOWN"
      },
      "title": "Caddy: MatchHost becomes case-sensitive for large host lists (\u003e100), enabling host-based route/auth bypass"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-27588",
    "datePublished": "2026-02-24T16:28:28.106Z",
    "dateReserved": "2026-02-20T17:40:28.450Z",
    "dateUpdated": "2026-02-24T16:28:28.106Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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