CVE-2026-72916 (GCVE-0-2026-72916)
Vulnerability from cvelistv5
Published
2026-08-10 21:19
Modified
2026-08-13 15:13
Severity ?
6.3 (Medium) - CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L
CWE
  • CWE-918 - Server-Side Request Forgery (SSRF)
  • CWE-1286 - Improper Validation of Syntactic Correctness of Input
Summary
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to loopback interfaces, potentially accessing private resources and services. Exploitation requires a system that supports the obsolete IPv4-compatible IPv6 mechanism. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1.
References
Impacted products
Vendor Product Version
mastodon mastodon Version: < 4.4.21
Version: >= 4.5.0-beta.1, < 4.5.14
Version: >= 4.6.0-beta.1, < 4.6.4
 Create a notification for this product.
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                "id": "CVE-2026-72916",
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                "timestamp": "2026-08-13T15:13:13.639949Z",
                "version": "2.0.3"
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          "value": "Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, PrivateAddressCheck.private_address? in app/lib/private_address_check.rb normalized IPv4-mapped IPv6 addresses but did not recognize IPv4-compatible IPv6 addresses with IPAddr#ipv4_compat?. An attacker could supply an address in the omitted range to bypass the ALLOWED_PRIVATE_ADDRESSES protection and make Mastodon send HTTP requests to loopback interfaces, potentially accessing private resources and services. Exploitation requires a system that supports the obsolete IPv4-compatible IPv6 mechanism. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1."
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            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
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            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
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      "references": [
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          "tags": [
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        {
          "name": "https://github.com/mastodon/mastodon/releases/tag/v4.4.21",
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          "tags": [
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          "url": "https://github.com/mastodon/mastodon/releases/tag/v4.5.14"
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          "name": "https://github.com/mastodon/mastodon/releases/tag/v4.6.4",
          "tags": [
            "x_refsource_MISC"
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        },
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          "tags": [
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          "url": "https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1"
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      "source": {
        "advisory": "GHSA-vwhj-3g83-v276",
        "discovery": "UNKNOWN"
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      "title": "Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses"
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    "dateReserved": "2026-08-10T17:57:26.143Z",
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    "state": "PUBLISHED"
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  "dataVersion": "5.2"
}


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