CVE-2026-4646Network attack vector

Plugin process crash via malformed PR URL

Published May 22, 2026 · Updated May 22, 2026

Improper input validation in Mattermost server releases allows remote authenticated users to crash the GitHub plugin process. The getPrsDetails path passes an unchecked PR URL to getRepoOwnerAndNameFromURL, which indexes the final two slash-delimited segments without confirming that they exist. An authenticated account can supply a malformed URL to the PR details endpoint when the GitHub plugin is enabled, terminating that plugin process without crashing the Mattermost server.

CVSS severity4.3
Medium
EPSS probability0.25%
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 Mattermost server releases allows remote authenticated users to crash the GitHub plugin process. The getPrsDetails path passes an unchecked PR URL to getRepoOwnerAndNameFromURL, which indexes the final two slash-delimited segments without confirming that they exist. An authenticated account can supply a malformed URL to the PR details endpoint when the GitHub plugin is enabled, terminating that plugin process without crashing the Mattermost server.

The record

CVE
CVE-2026-4646
Published
May 22, 2026
Updated
May 22, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-1287, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 22, 2026CVE publishedPublication date reported by the CVE source.
  2. May 22, 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=10.11.0 <=10.11.14
  2. Affected versionversion=11.4.0 <=11.4.4
  3. Affected versionversion=11.5.0 <=11.5.3
  4. Affected versionversion=11.6.0 <=11.6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.14; version=11.4.0 <=11.4.4; version=11.5.0 <=11.5.3; version=11.6.0 <=11.6.0

Published CVSS scores

4.3MattermostCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1287Improper Validation of Specified Type of Input
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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