GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration
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.

To clipboard 

{
  "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"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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

Author Source Type Date Other

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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.