Vulnerability from bitnami_vulndb
Published
2026-08-17 05:46
Modified
2026-08-17 06:10
Summary
Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses
Details

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, 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.

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Bitnami",
        "name": "mastodon",
        "purl": "pkg:bitnami/mastodon"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.4.21"
            },
            {
              "introduced": "4.5.0"
            },
            {
              "fixed": "4.5.14"
            },
            {
              "introduced": "4.6.0"
            },
            {
              "fixed": "4.6.4"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "severity": [
        {
          "score": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "type": "CVSS_V4"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-72916"
  ],
  "database_specific": {
    "cpes": [
      "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*"
    ],
    "severity": "Medium"
  },
  "details": "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, 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.",
  "id": "BIT-mastodon-2026-72916",
  "modified": "2026-08-17T06:10:32.268Z",
  "published": "2026-08-17T05:46:39.602Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/releases/tag/v4.4.21"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/releases/tag/v4.5.14"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/releases/tag/v4.6.4"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72916"
    }
  ],
  "schema_version": "1.6.2",
  "summary": "Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.