CVE-2026-45078

Service denial via uncapped WorkerLock retry intervals

Published May 28, 2026 · Updated May 28, 2026

Resource exhaustion in Element Synapse before 1.152.1 allows local authenticated users to deny service by starving request processing of CPU. The WaitingLock retry loop in synapse/handlers/worker_lock.py doubles an uncapped timeout after each timeout, eventually processing extremely large numeric intervals and consuming CPU needed by other requests. A local account on a homeserver that does not trust every local user is required; the bounded impact is failure of other users’ requests.

CVSS severity6.8
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Element Synapse before 1.152.1 allows local authenticated users to deny service by starving request processing of CPU. The WaitingLock retry loop in synapse/handlers/worker_lock.py doubles an uncapped timeout after each timeout, eventually processing extremely large numeric intervals and consuming CPU needed by other requests. A local account on a homeserver that does not trust every local user is required; the bounded impact is failure of other users’ requests.

The record

CVE
CVE-2026-45078
Published
May 28, 2026
Updated
May 28, 2026
Vendor
Element HQ
Product
Synapse
Classifications
CWE-770, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 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=< 1.152.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Element HQ · Synapseversion=< 1.152.1

Published CVSS scores

6.8GitHub, Inc.CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial of Service

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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