CVE-2022-39200Network attack vector

Modified event acceptance via missing signature check

Published Sep 12, 2022 · Updated Apr 23, 2025

Improper signature verification in Matrix.org Dendrite before 0.9.8 allows remote attackers to inject modified events through the /get_missing_events federation endpoint. In roomserver/internal/input/input_missing.go, the getMissingEvents loop converted untrusted events into processable events without calling VerifyEventSignatures, allowing invalid content to be cached and handled. Federation-disabled homeservers are not exposed, and other retrieval endpoints perform signature checks, limiting the issue to federated missing-event processing.

CVSS severity5.3
Medium
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper signature verification in Matrix.org Dendrite before 0.9.8 allows remote attackers to inject modified events through the /get_missing_events federation endpoint. In roomserver/internal/input/input_missing.go, the getMissingEvents loop converted untrusted events into processable events without calling VerifyEventSignatures, allowing invalid content to be cached and handled. Federation-disabled homeservers are not exposed, and other retrieval endpoints perform signature checks, limiting the issue to federated missing-event processing.

The record

CVE
CVE-2022-39200
Published
Sep 12, 2022
Updated
Apr 23, 2025
Vendor
Matrix.org
Product
Dendrite
Classifications
CWE-347, T1553
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 12, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record 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=< 0.9.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Matrix.org · Dendriteversion=< 0.9.8

Published CVSS scores

7.3GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
5.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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
T1553Subvert Trust Controls

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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