CVE-2021-37865Network attack vector

Service interruption via insufficiently constrained GIF processing

Published Jan 18, 2022 · Updated Dec 6, 2024

Resource exhaustion in Mattermost 6.2 and earlier allows remote authenticated users to interrupt the server through a crafted GIF upload. During draft-post uploads, the server's GIF-processing path insufficiently constrains work on a specially constructed image, consuming server resources. An account and permission to upload the file while drafting a post are required; the published record identifies server-side denial of service but does not distinguish a hang from a crash.

CVSS severity4.3
Medium
EPSS probability0.90%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Mattermost 6.2 and earlier allows remote authenticated users to interrupt the server through a crafted GIF upload. During draft-post uploads, the server's GIF-processing path insufficiently constrains work on a specially constructed image, consuming server resources. An account and permission to upload the file while drafting a post are required; the published record identifies server-side denial of service but does not distinguish a hang from a crash.

The record

CVE
CVE-2021-37865
Published
Jan 18, 2022
Updated
Dec 6, 2024
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-400, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 18, 2022CVE 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=unspecified <=6.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=unspecified <=6.2

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:N/A:P
5.7NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
4.3Mattermost, Inc.CVSS: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-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

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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