CVE-2021-37629Network attack vector

Share-token enumeration via unthrottled OCS requests

Published Sep 7, 2021 · Updated Aug 4, 2024

Missing throttling in Nextcloud Richdocuments before 3.8.4 and 4.0.0 through 4.2.0 allows attackers to enumerate potentially valid share tokens. The public OCS endpoint processes repeated candidate share tokens without throttling invalid attempts, creating an enumeration oracle. Unauthenticated remote access is sufficient; successful probing identifies potentially usable tokens but does not itself read or modify shared files.

CVSS severity5.3
Medium
EPSS probability1.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing throttling in Nextcloud Richdocuments before 3.8.4 and 4.0.0 through 4.2.0 allows attackers to enumerate potentially valid share tokens. The public OCS endpoint processes repeated candidate share tokens without throttling invalid attempts, creating an enumeration oracle. Unauthenticated remote access is sufficient; successful probing identifies potentially usable tokens but does not itself read or modify shared files.

The record

CVE
CVE-2021-37629
Published
Sep 7, 2021
Updated
Aug 4, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Security Advisories
Classifications
CWE-200, CWE-799, CWE-770, T1110
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=< 3.8.4
  2. Affected versionversion=>= 4.0.0, < 4.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Security Advisoriesversion=< 3.8.4; version=>= 4.0.0, < 4.2.1

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-200Exposure of Sensitive Information to an Unauthorized Actor
CWE-799Improper Control of Interaction Frequency
CWE-770Allocation of Resources Without Limits or Throttling
T1110Brute Force

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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