Mattermost Bot Registration Validation Bypass 10.11-11.6, Unprivileged Intercept
CVE-2026-6046 Published on June 12, 2026
Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649
Vulnerability Analysis
CVE-2026-6046 is exploitable with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity and availability.
Weakness Type
What is an Information Disclosure Vulnerability?
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CVE-2026-6046 has been classified to as an Information Disclosure vulnerability or weakness.
Products Associated with CVE-2026-6046
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Affected Versions
Mattermost:- Version 11.6.0, <= 11.6.1 is affected.
- Version 11.5.0, <= 11.5.4 is affected.
- Version 10.11.0, <= 10.11.15 is affected.
- Version 10.11.0, <= 10.11.16 is affected.
- Version 11.7.0 is unaffected.
- Version 11.6.2 is unaffected.
- Version 11.5.5 is unaffected.
- Version 10.11.16 is unaffected.
- Version 10.11.17 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.