CVE-2017-18891Network attack vector

Phishing via Markdown links on error pages

Published Jun 19, 2020 · Updated Aug 5, 2024

Open redirect in Mattermost Server before 4.0.5, 4.1.1, and 4.2.0 allows remote attackers to place phishing links on error pages. The error-page flow accepted title and message query parameters containing Markdown and rendered attacker-controlled external links. A victim must open the crafted error-page URL and select its link, which sends the browser away from the trusted Mattermost origin.

CVSS severity6.1
Medium
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Mattermost Server before 4.0.5, 4.1.1, and 4.2.0 allows remote attackers to place phishing links on error pages. The error-page flow accepted title and message query parameters containing Markdown and rendered attacker-controlled external links. A victim must open the crafted error-page URL and select its link, which sends the browser away from the trusted Mattermost origin.

The record

CVE
CVE-2017-18891
Published
Jun 19, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-601, T1204.001
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

5.8NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:P/I:P/A:N
6.1NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/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.

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-601URL Redirection to Untrusted Site ('Open Redirect')
T1204.001Malicious Link

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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