CVE-2026-28432Network attack vector

Federated actor impersonation via HTTP signature bypass

Published Mar 9, 2026 · Updated Mar 9, 2026

Improper HTTP signature verification in Misskey before 2026.3.1 allows remote attackers to submit forged federation requests. The exact verification locus and the incorrect operation on attacker-controlled signature data remain intentionally undisclosed by the project. The flaw affects every server even when federation is disabled; exploitation is network-reachable and requires passive user interaction, with unauthorized data changes and limited disclosure.

CVSS severity7.1
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper HTTP signature verification in Misskey before 2026.3.1 allows remote attackers to submit forged federation requests. The exact verification locus and the incorrect operation on attacker-controlled signature data remain intentionally undisclosed by the project. The flaw affects every server even when federation is disabled; exploitation is network-reachable and requires passive user interaction, with unauthorized data changes and limited disclosure.

The record

CVE
CVE-2026-28432
Published
Mar 9, 2026
Updated
Mar 9, 2026
Vendor
Misskey Project
Product
Misskey
Classifications
CWE-347, T1656
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2026.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Misskey Project · Misskeyversion=< 2026.3.1

Published CVSS scores

7.1GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1656Impersonation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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