CVE-2024-25623

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

HIGH

7.7

CVSS Score

Published: February 19, 2024 at 03:28 PM UTC

Updated: June 17, 2026 at 07:16 AM UTC

2 products affected across 2 vendorsMastodonMastodon

Using mastodon by mastodon?

Get instant alerts when new vulnerabilities affect mastodon - before attackers find them.

Real-time alertsTrack your software stackFree plan available

Start Free Sign In

Severity

HIGH7.7

Exploit prediction

EPSS 0.5%

SSVC

No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mastodon · Joinmastodon

95%

v < 3.5.194.0.0 ≤ v < 4.0.154.1.0 ≤ v < 4.1.154.2.0 ≤ v < 4.2.7

Affected range stops below 3.5.19, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.0.15, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.15, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.7, so it looks safe — our inference, not a vendor statement

Mastodon · Mastodon

60%

v < 3.5.19v < 4.0.15v < 4.1.15v < 4.2.7

Affected range stops below 3.5.19, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.0.15, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.15, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.7, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

x_refsource_MISCPatch

Source: [email protected]

https://github.com/mastodon/mastodon/commit/9fee5e852669e26f970e278021302e1a203fc022

x_refsource_CONFIRMVendor Advisory

Source: [email protected]

https://github.com/mastodon/mastodon/security/advisories/GHSA-jhrq-qvrm-qr36

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.7HIGH[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: LOW
User Interaction: NONE
Scope: CHANGED
Confidentiality: NONE
Integrity: HIGH
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-434

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create account Sign in

Free plan, no card