CVE-2024-52815Network attack vector

User sync interruption via malformed federation invite

Published Dec 3, 2024 · Updated Dec 3, 2024

Improper input validation in Element HQ Synapse before 1.120.1 allows remote attackers to interrupt an invited user's sync via federation. Federation invite handling accepts a non-list invite_room_state value, and the sync encoder passes it to list() instead of rejecting or discarding it. A remote attacker must control a federating homeserver and send the malformed invite; the resulting failure blocks /sync for the targeted user.

CVSS severity8.7
High
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Element HQ Synapse before 1.120.1 allows remote attackers to interrupt an invited user's sync via federation. Federation invite handling accepts a non-list invite_room_state value, and the sync encoder passes it to list() instead of rejecting or discarding it. A remote attacker must control a federating homeserver and send the malformed invite; the resulting failure blocks /sync for the targeted user.

The record

CVE
CVE-2024-52815
Published
Dec 3, 2024
Updated
Dec 3, 2024
Vendor
Element HQ
Product
Synapse
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 3, 2024CVE publishedPublication date reported by the CVE source.
  2. Dec 3, 2024Record 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 <1.120.1
  2. Affected versionversion=< 1.120.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Element HQ · Synapseversion=0 <1.120.1; version=< 1.120.1

Published CVSS scores

8.7GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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

T1499.004Application or System Exploitation

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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