Mastodon
CVE-2026-23964
MEDIUM
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Lifecycle Timeline
2DescriptionGitHub Advisory
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.
AnalysisAI
Mastodon is a free, open-source social network server based on ActivityPub. [CVSS 6.5 MEDIUM]
Technical ContextAI
Classified as CWE-863 (Incorrect Authorization). Affects the web push subscription update component of Mastodon. 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 ano
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
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Same weakness CWE-863 – Incorrect Authorization
View allSame technique Authentication Bypass
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External POC / Exploit Code
Leaving vuln.today