Lack of media type verification of Activity Streams objects allows impersonation of remote accounts
Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.2.7, 4.1.15, 4.0.15, and 3.5.19, when fetching remote statuses, Mastodon doesn't check that the response from the remote server has a `Content-Type` header value of the Activity Streams media type, which allows a threat actor to upload a crafted Activity Streams document to a remote server and make a Mastodon server fetch it, if the remote server accepts arbitrary user uploads. The vulnerability allows a threat actor to impersonate an account on a remote server that satisfies all of the following properties: allows the attacker to register an account; accepts arbitrary user-uploaded documents and places them on the same domain as the ActivityPub actors; and serves user-uploaded document in response to requests with an `Accept` header value of the Activity Streams media type. Versions 4.2.7, 4.1.15, 4.0.15, and 3.5.19 contain a fix for this issue.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2024-25623
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 2 Nov 2026, 17:11 UTC · Revision 1
Source evidence
Lack of media type verification of Activity Streams objects allows impersonation of remote accounts
core-osv · Original sourcePublished 19 Feb 2024, 15:28 UTC
Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.2.7, 4.1.15, 4.0.15, and 3.5.19, when fetching remote statuses, Mastodon doesn't check that the response from the remote server has a `Content-Type` header value of the Activity Streams media type, which allows a threat actor to upload a crafted Activity Streams document to a remote server and make a Mastodon server fetch it, if the remote server accepts arbitrary user uploads. The vulnerability allows a threat actor to impersonate an account on a remote server that satisfies all of the following properties: allows the attacker to register an account; accepts arbitrary user-uploaded documents and places them on the same domain as the ActivityPub actors; and serves user-uploaded document in response to requests with an `Accept` header value of the Activity Streams media type. Versions 4.2.7, 4.1.15, 4.0.15, and 3.5.19 contain a fix for this issue.
osv:CVE-2024-25623
Complete source record
{
"id": "8d2b5b5812a3724bd22c00bda53eb081ffbfd2e016dd9f0a4d65f44abbae2664",
"url": "https://osv.dev/vulnerability/CVE-2024-25623",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Lack of media type verification of Activity Streams objects allows impersonation of remote accounts",
"summary": "Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.2.7, 4.1.15, 4.0.15, and 3.5.19, when fetching remote statuses, Mastodon doesn't check that the response from the remote server has a `Content-Type` header value of the Activity Streams media type, which allows a threat actor to upload a crafted Activity Streams document to a remote server and make a Mastodon server fetch it, if the remote server accepts arbitrary user uploads. The vulnerability allows a threat actor to impersonate an account on a remote server that satisfies all of the following properties: allows the attacker to register an account; accepts arbitrary user-uploaded documents and places them on the same domain as the ActivityPub actors; and serves user-uploaded document in response to requests with an `Accept` header value of the Activity Streams media type. Versions 4.2.7, 4.1.15, 4.0.15, and 3.5.19 contain a fix for this issue.",
"evidence": "osv:CVE-2024-25623",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2024-25623",
"aliases": [
"BIT-mastodon-2024-25623",
"CVE-2024-25623",
"GHSA-jhrq-qvrm-qr36"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/mastodon/mastodon",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "e9123ad691727ffec3672ff3912ef56e67c930ef"
},
{
"introduced": "fb389bd73c8a4bc2924496f6041c8eee27572d21"
},
{
"fixed": "e5726d211fd3dc1d640f202e808e25891d765586"
},
{
"introduced": "61c5dfb9295ea66c376c452a7ef7379e8c562416"
},
{
"fixed": "b7b03e8d26a4344ef331ba667c16311110a0d6dd"
},
{
"introduced": "4fcc026f0f1b12a9de21a3af33375a9c8867dd55"
},
{
"fixed": "0e4e98fad1e21e4f356b3a71eef3fca79890105c"
},
{
"fixed": "9fee5e852669e26f970e278021302e1a203fc022"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "3.5.19"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "4.0.0"
},
{
"fixed": "4.0.15"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "4.1.0"
},
{
"fixed": "4.1.15"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "4.2.0"
},
{
"fixed": "4.2.7"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "9fee5e852669e26f970e278021302e1a203fc022"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"v3.5.18",
"v4.0.14",
"v4.1.14",
"v4.2.6",
"v3.5.17",
"v4.0.13",
"v4.1.13",
"v4.2.5",
"v3.5.16",
"v4.0.12",
"v4.1.12",
"v4.2.4",
"v4.2.3",
"v4.1.11",
"v4.2.2",
"v4.1.10",
"v3.5.15",
"v4.2.1",
"v4.2.0",
"v4.0.11",
"v3.5.14",
"v4.1.9",
"v4.0.10",
"v4.1.8",
"v4.1.7",
"v4.0.9",
"v3.5.13",
"v3.5.12",
"v4.0.8",
"v4.1.6",
"v3.5.11",
"v4.0.7",
"v4.1.5",
"v4.0.6",
"v3.5.10",
"v4.1.4",
"v4.1.3",
"v4.0.5",
"v3.5.9",
"v3.5.8",
"v4.0.4",
"v4.1.2",
"v4.1.1",
"v4.0.3",
"v3.5.7",
"v3.5.6",
"v4.0.2",
"v4.1.0",
"v3.5.5",
"v4.0.1",
"v3.5.4",
"v4.0.0",
"v3.5.3",
"v3.5.2",
"v3.5.1",
"v3.5.0",
"v3.5.0rc3",
"v3.5.0rc2",
"v3.5.0rc1",
"v3.3.0",
"v3.4.1",
"v3.4.0",
"v3.4.0rc2",
"v3.4.0rc1",
"v3.3.0rc3",
"v3.3.0rc2",
"v3.3.0rc1",
"v3.2.0",
"v3.2.0rc2",
"v3.2.0rc1",
"v3.1.4",
"v3.1.3",
"v3.1.2",
"v3.0.1",
"v3.1.1",
"v3.1.0",
"v3.1.0rc2",
"v3.1.0rc1",
"v3.0.0",
"v3.0.0rc3",
"v3.0.0rc2",
"v3.0.0rc1",
"v2.9.2",
"v2.9.1",
"v2.9.0",
"v2.9.0rc2",
"v2.9.0rc1",
"v2.8.2",
"v2.8.1",
"v2.8.0",
"v2.8.0rc3",
"v2.8.0rc2",
"v2.8.0rc1",
"v2.7.1",
"v2.7.0",
"v2.7.0rc3",
"v2.7.0rc2",
"v2.7.0rc1",
"v2.6.1",
"v2.6.0",
"v2.6.0rc4",
"v2.6.0rc3",
"v2.6.0rc2",
"v2.6.0rc1",
"v2.5.0",
"v2.5.0rc2",
"v2.5.0rc1",
"v2.4.3",
"v2.4.3rc3",
"v2.4.3rc2",
"v2.4.3rc1",
"v2.4.2",
"v2.4.2rc3",
"v2.4.2rc2",
"v2.4.2rc1",
"v2.4.1",
"v2.4.1rc4",
"v2.4.1rc3",
"v2.4.1rc2",
"v2.4.1rc1",
"v2.4.0",
"v2.4.0rc5",
"v2.4.0rc4",
"v2.4.0rc3",
"v2.4.0rc2",
"v2.4.0rc1",
"v2.3.2",
"v2.3.2rc5",
"v2.3.2rc4",
"v2.3.2rc3",
"v2.3.2rc2",
"v2.3.2rc1",
"v2.3.1",
"v2.3.1rc3",
"v2.3.1rc2",
"v2.3.1rc1",
"v2.3.0",
"v2.3.0rc3",
"v2.3.0rc2",
"v2.3.0rc1",
"v2.2.0",
"v2.2.0rc2",
"v2.2.0rc1",
"v2.1.3",
"v2.1.2",
"v2.1.1",
"v2.1.0",
"v2.1.0rc6",
"v2.1.0rc5",
"v2.1.0rc4",
"v2.1.0rc3",
"v2.1.0rc2",
"v2.1.0rc1",
"v2.0.0",
"v2.0.0rc4",
"v2.0.0rc3",
"v2.0.0rc2",
"v2.0.0rc1",
"v1.6.1",
"v1.6.0",
"v1.6.0rc5",
"v1.6.0rc4",
"v1.6.0rc3",
"v1.6.0rc2",
"v1.6.0rc1",
"v1.5.1",
"v1.5.0",
"v1.5.0rc3",
"v1.5.0rc2",
"v1.5.0rc1",
"v1.4.7",
"v1.4.6",
"v1.4.5",
"v1.4.4",
"v1.4.3",
"v1.4.2",
"v1.4.1",
"v1.4rc6",
"v1.4rc5",
"v1.4rc4",
"v1.4rc3",
"v1.4rc2",
"v1.4rc1",
"v1.3.2",
"v1.3.1",
"v1.3",
"v1.2.2",
"v1.2.1",
"v1.2",
"v1.1.2",
"v1.1.1",
"v1.1",
"v1.0",
"v0.9.9",
"v0.9",
"v0.8",
"v0.7",
"v0.6",
"v0.1.2",
"v0.1.1",
"v0.1.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-25623.json"
}
}
],
"modified": "2026-10-28T02:30:21.376718320Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/25xxx/CVE-2024-25623.json",
"https://github.com/mastodon/mastodon/security/advisories/GHSA-jhrq-qvrm-qr36",
"https://nvd.nist.gov/vuln/detail/CVE-2024-25623",
"https://github.com/mastodon/mastodon/commit/9fee5e852669e26f970e278021302e1a203fc022"
],
"provider_metadata": {
"cwe_ids": [
"CWE-434"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/25xxx/CVE-2024-25623.json"
}
},
"related_cves": [
{
"value": "CVE-2024-25623",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 487571,
"published_at": "2024-02-19T15:28:15.296+00:00"
}