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CVE-2026-48028

Mastodon: Removal of integrity-protected JSON entries from signed activities

Medium6.5EPSS 0.18%
Published
Updated
Reserved
Assigned by
GitHub_M

Description

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.

Scores

CVSS scores of CVE-2026-48028, by who scored it
Scored byCVSSScoreVector
GitHub_MCNA (assigner)3.1Medium6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
NVDNVD · Deferred3.1Medium6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
EPSS (exploitation in 30 days)
0.18% · top 93% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.

Weakness

Affected products

  • mastodon · mastodon

    • affected >= 4.5.0-beta.1, < 4.5.10
    • affected >= 4.4.0-beta.1, < 4.4.17
    • affected < 4.3.23

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .