CVE-2026-23964

6.5 MEDIUM
Published: January 22, 2026 Modified: February 02, 2026
View on NVD

Description

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.5.5, 4.4.12, and 4.3.18, an insecure direct object reference in the web push subscription update endpoint lets any authenticated user update another user's push subscription by guessing or obtaining the numeric subscription id. This can be used to disrupt push notifications for other users and also leaks the web push subscription endpoint. Any user with a web push subscription is impacted, because another authenticated user can tamper with their push subscription settings if they can guess or obtain the subscription id. This allows an attacker to disrupt push notifications by changing the policy (whether to filter notifications from non-followers or non-followed users) and subscribed notification types of their victims. Additionally, the endpoint returns the subscription object, which includes the push notification endpoint for this subscription, but not its keypair. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.3.18
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.4.12
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.5.5
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/security/advisories/GHSA-f3q8-7vw3-69v4
Source: security-advisories@github.com
Vendor Advisory

4 reference(s) from NVD

Quick Stats

CVSS v3 Score
6.5 / 10.0
EPSS (Exploit Probability)
0.0%
11th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

joinmastodon