CVE-2026-2457
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Post Metadata Spoofing in Mattermost via Unsanitized PUT Requests

Publication date: 2026-03-16

Last updated on: 2026-03-18

Assigner: Mattermost, Inc.

Description
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to sanitize client-supplied post metadata which allows an authenticated attacker to spoof permalink embeds impersonating other users via crafted PUT requests to the post update API endpoint.. Mattermost Advisory ID: MMSA-2025-00569
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Meta Information
Published
2026-03-16
Last Modified
2026-03-18
Generated
2026-06-16
AI Q&A
2026-03-16
EPSS Evaluated
2026-06-15
NVD
CVE-2026-2457
EUVD
EUVD-2026-12407
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
mattermost mattermost_server From 10.11.0 (inc) to 10.11.11 (exc)
mattermost mattermost_server From 11.2.0 (inc) to 11.2.3 (exc)
mattermost mattermost_server From 11.3.0 (inc) to 11.3.1 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-346 The product does not properly verify that the source of data or communication is valid.
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Executive Summary

This vulnerability exists in certain versions of Mattermost (11.3.x <= 11.3.0, 11.2.x <= 11.2.2, and 10.11.x <= 10.11.10) where the software fails to properly sanitize client-supplied post metadata.

Because of this, an authenticated attacker can craft PUT requests to the post update API endpoint that spoof permalink embeds, making it appear as if other users are impersonating those posts.

Impact Analysis

The impact of this vulnerability is that an authenticated attacker can impersonate other users by spoofing permalink embeds in posts.

This could lead to misinformation, confusion, or manipulation within the Mattermost communication platform, potentially damaging trust among users.

The CVSS score of 4.3 indicates a low to medium severity impact, specifically affecting integrity without impacting confidentiality or availability.

Compliance Impact

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Detection Guidance

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