CVE-2023-1776Network attack vector

Stored XSS via malicious SVG card attachment

Published Mar 31, 2023 · Updated Dec 6, 2024

Stored XSS in Mattermost 3.3.0 through 7.7.1 allows remote authenticated users to execute script via a Boards card attachment. The Boards attachment path accepts a crafted SVG and makes it available at a direct file URL without neutralizing active web content. An authenticated attacker must upload the file and persuade another user to open its direct link, causing attacker-controlled script to run in that user's browser context.

CVSS severity5.4
Medium
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Mattermost 3.3.0 through 7.7.1 allows remote authenticated users to execute script via a Boards card attachment. The Boards attachment path accepts a crafted SVG and makes it available at a direct file URL without neutralizing active web content. An authenticated attacker must upload the file and persuade another user to open its direct link, causing attacker-controlled script to run in that user's browser context.

The record

CVE
CVE-2023-1776
Published
Mar 31, 2023
Updated
Dec 6, 2024
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 31, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 6, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.3.0 <=7.1.5
  2. Affected versionversion=3.3.0 <=7.7.1
  3. Affected versionversion=3.3.0 <7.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=3.3.0 <=7.1.5; version=3.3.0 <=7.7.1; version=3.3.0 <7.8.0

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
7.3Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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