CVE-2017-18883Network attack vector

OAuth authorization-data prediction

Published Jun 19, 2020 · Updated Aug 5, 2024

Insufficient entropy in Mattermost Server 4.1.1 and earlier, 4.2.0, and 4.3.0-rc1 allows remote attackers to predict OAuth authorization data. Mattermost has not published which authorization value or generator lacks entropy, so the exact faulty operation remains undisclosed. Exposure requires Mattermost to act as an OAuth 2.0 service provider; published records do not identify the precise access gained.

CVSS severity9.1
Critical
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient entropy in Mattermost Server 4.1.1 and earlier, 4.2.0, and 4.3.0-rc1 allows remote attackers to predict OAuth authorization data. Mattermost has not published which authorization value or generator lacks entropy, so the exact faulty operation remains undisclosed. Exposure requires Mattermost to act as an OAuth 2.0 service provider; published records do not identify the precise access gained.

The record

CVE
CVE-2017-18883
Published
Jun 19, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-331
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 19, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
6.4NVDAV:N/AC:L/Au:N/C:P/I:P/A:N
6.9GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-331Insufficient Entropy

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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