Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, Mastodon's normalization of incoming activities signed with Linked-Data Signatures does not sufficiently protect the activities from a certain class of spoofing, allowing threat actors to remove JSON entries from valid signed activities from a third-party actor. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.
{
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48028.json",
"cwe_ids": [
"CWE-354"
],
"cna_assigner": "GitHub_M"
}{
"extracted_events": [
{
"introduced": "4.5.0-beta.1"
},
{
"fixed": "4.5.10"
},
{
"introduced": "4.4.0-beta.1"
},
{
"fixed": "4.4.17"
},
{
"introduced": "0"
},
{
"fixed": "4.3.23"
}
],
"source": "AFFECTED_FIELD"
}