Improper Verification of Cryptographic Signature in Mastodon - CVE-2026-46349
Published: May 23, 2026
Vulnerability identifier: #VU132182
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-46349
CWE-ID: CWE-347
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to spoof activity integrity.
The vulnerability exists due to improper verification of cryptographic signature in Linked-Data Signature normalization of incoming activities when processing signed JSON-LD activities. A remote attacker can re-arrange a valid signed JSON-LD activity from a third-party actor to have it processed differently to spoof activity integrity.
The demonstrated impact is limited to re-issuing retracted boost (Announce) activities from a third-party user without their involvement.
Affected software
Mastodon
How to mitigate CVE-2026-46349
Install security update from vendor's website.
Mastodon - addressed in versions 4.3.23, 4.4.17, 4.5.10