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TI-2024-16851 Aliases CVE-2024-25623

Lack of media type verification of Activity Streams objects allows impersonation of remote accounts

Priority LOW 37CWE-434Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
Low · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-434.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00511 43rd percentileScored 2026-11-07
Fix Fixed mastodon (mastodon): 3.5.19, 4.0.15, 4.1.15 +1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mastodonmastodonbefore 3.5.19; 4.0.0 to before 4.0.15; 4.1.0 to before 4.1.15; 4.2.0 to before 4.2.73.5.19, 4.0.15, 4.1.15, 4.2.7Patch availableCNA
  • mastodon Vendormastodon Affected before 3.5.19; 4.0.0 to before 4.0.15; 4.1.0 to before 4.1.15; 4.2.0 to before 4.2.7 Fixed in 3.5.19, 4.0.15, 4.1.15, 4.2.7 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*before 3.5.19; 4.0.0 to before 4.0.15; 4.1.0 to before 4.1.15; 4.2.0 to before 4.2.7Vulnerablemastodon
  • cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:* Versions before 3.5.19; 4.0.0 to before 4.0.15; 4.1.0 to before 4.1.15; 4.2.0 to before 4.2.7 Vulnerable ·mastodon

Remediation

  • Fix · CNA mastodon (mastodon) Fixed in 3.5.19, 4.0.15, 4.1.15, 4.2.7

Timeline

  1. 2026-10-02 Threatist record created from CVE-2024-25623

References

Patch 1

Advisory 1

  • TI-2022-02004 Improper Restriction of Excessive Authentication Attempts in mastodon/mastodon CVSS 3.1CRITICAL 9.8
  • TI-2025-34613 Mastodon e‑mail throttle misconfiguration allows unlimited email confirmations against unconfirmed emails CVSS 3.1HIGH 7.5
  • TI-2022-22936 Mastodon through 4.0.2 allows attackers to cause a denial of service (large Sidekiq pull… CVSS 3.1HIGH 7.5
  • TI-2023-18301 Mastodon vulnerable to arbitrary file creation through media attachments CVSS 3.1CRITICAL 10.0
  • TI-2023-13359 Mastodon's blind LDAP injection in login allows the attacker to leak arbitrary attributes from LDAP database CVSS 3.1HIGH 7.7
  • TI-2024-16846 External OpenID Connect Account Takeover by E-Mail Change in mastodon CVSS 3.1HIGH 7.4
See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences