{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-54740",
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "state": "PUBLISHED",
        "assignerShortName": "GitHub_M",
        "dateReserved": "2026-06-15T23:07:33.233Z",
        "datePublished": "2026-08-19T20:14:29.391Z",
        "dateUpdated": "2026-08-20T19:57:12.849Z"
    },
    "containers": {
        "cna": {
            "title": "Lemmy: Lower-ranked federated moderator can remove higher-ranked moderators",
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-862",
                            "lang": "en",
                            "description": "CWE-862: Missing Authorization",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "attackComplexity": "LOW",
                        "attackVector": "NETWORK",
                        "availabilityImpact": "NONE",
                        "baseScore": 6.5,
                        "baseSeverity": "MEDIUM",
                        "confidentialityImpact": "NONE",
                        "integrityImpact": "HIGH",
                        "privilegesRequired": "LOW",
                        "scope": "UNCHANGED",
                        "userInteraction": "NONE",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N",
                        "version": "3.1"
                    }
                }
            ],
            "references": [
                {
                    "name": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7",
                    "tags": [
                        "x_refsource_CONFIRM"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7"
                },
                {
                    "name": "https://github.com/LemmyNet/lemmy/pull/6475",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/pull/6475"
                },
                {
                    "name": "https://github.com/LemmyNet/lemmy/pull/6478",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/pull/6478"
                },
                {
                    "name": "https://github.com/LemmyNet/lemmy/commit/d127e714a66f34f6b9c8ea15f20097ac907cdf28",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/commit/d127e714a66f34f6b9c8ea15f20097ac907cdf28"
                },
                {
                    "name": "https://github.com/LemmyNet/lemmy/commit/ede1d348344ca2027fd1bc6a0cab25575c0c3a4c",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/commit/ede1d348344ca2027fd1bc6a0cab25575c0c3a4c"
                },
                {
                    "name": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.19",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.19"
                },
                {
                    "name": "https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18"
                },
                {
                    "name": "https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19"
                }
            ],
            "affected": [
                {
                    "vendor": "LemmyNet",
                    "product": "lemmy",
                    "versions": [
                        {
                            "version": "< 0.19.19",
                            "status": "affected"
                        },
                        {
                            "version": ">= 1.0.0-alpha.0, < 1.0.0-alpha.18",
                            "status": "affected"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
                "shortName": "GitHub_M",
                "dateUpdated": "2026-08-19T20:14:29.391Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, a lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. The local API uses LocalUser::is_higher_mod_or_admin_check to enforce moderator rank, but CollectionRemove::verify in crates/apub/activities/src/community/collection_remove.rs only calls verify_mod_action. CollectionRemove::receive dereferences self.object as an ApubPerson, creates a CommunityModeratorForm, and calls CommunityActions::leave without checking that the actor outranks the moderator identified by the object field. In communities with federated moderators, a junior moderator can therefore strip senior moderators from the community moderator list even though the local API rejects the same action. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18."
                }
            ],
            "source": {
                "advisory": "GHSA-xmpx-2j2f-c7g7",
                "discovery": "UNKNOWN"
            }
        },
        "adp": [
            {
                "references": [
                    {
                        "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7",
                        "tags": [
                            "exploit"
                        ]
                    }
                ],
                "metrics": [
                    {
                        "other": {
                            "type": "ssvc",
                            "content": {
                                "timestamp": "2026-08-20T19:57:07.165095Z",
                                "id": "CVE-2026-54740",
                                "options": [
                                    {
                                        "Exploitation": "poc"
                                    },
                                    {
                                        "Automatable": "no"
                                    },
                                    {
                                        "Technical Impact": "partial"
                                    }
                                ],
                                "role": "CISA Coordinator",
                                "version": "2.0.3"
                            }
                        }
                    }
                ],
                "title": "CISA ADP Vulnrichment",
                "providerMetadata": {
                    "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
                    "shortName": "CISA-ADP",
                    "dateUpdated": "2026-08-20T19:57:12.849Z"
                }
            }
        ]
    }
}