Misskey: JSON-LD signature validation + compaction may lead to improper activity handling

published 2026-08-03 3 mo ago modified 2026-10-23 16 d ago also EUVD-2026-52485

cvss: 9.2; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits: 0; none known

Misskey is an open source, federated social media platform. Versions 12.37.0 and later, but prior to 2026.5.4, contain a vulnerability in the JSON-LD signature validation and compaction process that allows spoofed activities to be accepted as valid. This issue has been fixed in version 2026.5.4.

Patch / fix

fixed in 1 links 1

misskey misskey 2026.5.4

github.com/misskey-dev/misskey/releases/tag/2026.5.4 release

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 3 mo ago (2026-08-04)

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	9.2	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:H/SA:N
CNA	4.0	9.2	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

misskey-dev misskey

Classification

Weakness

CWE-347 Improper Verification of Cryptographic Signature

References

Sources

CVE List CVE-2026-46713
NVD CVE-2026-46713

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary