CVE-2026-72916 (GCVE-0-2026-72916)

Vulnerability from cvelistv5 – Published: 2026-08-10 21:19 – Updated: 2026-08-10 21:19
VLAI
Title
Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses
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.
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
Assigner
References
Impacted products
Vendor Product Version
mastodon mastodon Affected: < 4.4.21
Affected: >= 4.5.0-beta.1, < 4.5.14
Affected: >= 4.6.0-beta.1, < 4.6.4
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "mastodon",
          "vendor": "mastodon",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.4.21"
            },
            {
              "status": "affected",
              "version": "\u003e= 4.5.0-beta.1, \u003c 4.5.14"
            },
            {
              "status": "affected",
              "version": "\u003e= 4.6.0-beta.1, \u003c 4.6.4"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "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."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "HIGH",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "LOW",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "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"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-918",
              "description": "CWE-918: Server-Side Request Forgery (SSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-1286",
              "description": "CWE-1286: Improper Validation of Syntactic Correctness of Input",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-10T21:19:02.908Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276"
        },
        {
          "name": "https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892"
        },
        {
          "name": "https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074"
        },
        {
          "name": "https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b"
        },
        {
          "name": "https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d"
        },
        {
          "name": "https://github.com/mastodon/mastodon/releases/tag/v4.4.21",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/releases/tag/v4.4.21"
        },
        {
          "name": "https://github.com/mastodon/mastodon/releases/tag/v4.5.14",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/releases/tag/v4.5.14"
        },
        {
          "name": "https://github.com/mastodon/mastodon/releases/tag/v4.6.4",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/releases/tag/v4.6.4"
        },
        {
          "name": "https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1"
        }
      ],
      "source": {
        "advisory": "GHSA-vwhj-3g83-v276",
        "discovery": "UNKNOWN"
      },
      "title": "Mastodon: SSRF Protection Bypass via IPv4-compatible IPv6 Addresses"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-72916",
    "datePublished": "2026-08-10T21:19:02.908Z",
    "dateReserved": "2026-08-10T17:57:26.143Z",
    "dateUpdated": "2026-08-10T21:19:02.908Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-72916",
      "date": "2026-08-12",
      "epss": "0.00359",
      "percentile": "0.28835"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-72916\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-08-10T22:17:10.510\",\"lastModified\":\"2026-08-10T22:17:10.510\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"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.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"mastodon\",\"product\":\"mastodon\",\"versions\":[{\"version\":\"\u003c 4.4.21\",\"status\":\"affected\"},{\"version\":\"\u003e= 4.5.0-beta.1, \u003c 4.5.14\",\"status\":\"affected\"},{\"version\":\"\u003e= 4.6.0-beta.1, \u003c 4.6.4\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"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/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\",\"baseScore\":6.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"NONE\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"LOW\",\"subIntegrityImpact\":\"LOW\",\"subAvailabilityImpact\":\"LOW\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-918\"},{\"lang\":\"en\",\"value\":\"CWE-1286\"}]}],\"references\":[{\"url\":\"https://github.com/mastodon/mastodon/commit/18c61f286f1f5718a8f517940ba384866ffa3892\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/commit/467c933459c7d0e5513475b9e4888afaedfb1074\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/commit/930aa9fee26bf9eaefe27826fa1061288d83373b\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/commit/da47a1bd3cd07935d7ca55a1f4f1a76f7f167e0d\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/releases/tag/v4.4.21\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/releases/tag/v4.5.14\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/releases/tag/v4.6.4\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/releases/tag/v4.7.0-beta.1\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/mastodon/mastodon/security/advisories/GHSA-vwhj-3g83-v276\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}



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.