CVE-2026-6850

Q: How do I fix CVE-2026-6850?

Upgrade mattermost server to 11.7.3 or later.

Q: Is CVE-2026-6850 being actively exploited?

Not that we know of. CVE-2026-6850 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 15% of all scored CVEs.

Q: How severe is CVE-2026-6850?

CVE-2026-6850 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2026-6850 affect?

Published advisories record a fix for mattermost server (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

MEDIUM

6.5

CVSS v3

NVD

Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658

CWE-1333

How to fix

Remediation Available

mattermost serverNVD

Affected:>= 11.7.0, < 11.7.3Fixed in:11.7.3CVE-2026-6850derived from NVD

Affected:>= 10.11.0, < 10.11.20Fixed in:10.11.20CVE-2026-6850derived from NVD

Affected:>= 11.6.0, < 11.6.5Fixed in:11.6.5CVE-2026-6850derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

0.24%probability of exploitation in 30 days

15thpercentile

Low risk: more likely to be exploited than 15% of all known CVEs.

References

Vendor Advisory1

mattermost.com

Related Vulnerabilities

Other CWE-1333 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-3364	High	7.5	44%	-	Fix
CVE-2024-8124	High	7.5	40%	-	Fix
CVE-2024-25126	Medium	5.3	35%	-	Fix
CVE-2024-2651	Medium	6.5	33%	-	Fix
CVE-2021-32837	High	7.5	29%	-	Fix
CVE-2024-2829	High	7.5	26%	-	Fix

Common questions

How do I fix CVE-2026-6850?

Upgrade mattermost server to 11.7.3 or later.

Is CVE-2026-6850 being actively exploited?

Not that we know of. CVE-2026-6850 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 15% of all scored CVEs.

How severe is CVE-2026-6850?

CVE-2026-6850 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-6850 affect?

Published advisories record a fix for mattermost server (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2026-6850

Markdown

[![CVE-2026-6850](https://tridentstack.com/cve/badge/CVE-2026-6850.svg)](https://tridentstack.com/cve/CVE-2026-6850)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-6850"><img src="https://tridentstack.com/cve/badge/CVE-2026-6850.svg" alt="CVE-2026-6850"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-13.