CVE-2021-29453Known exploitationNetwork attack vector

Service interruption via unbounded image thumbnail decoding

Published Apr 19, 2021 · Updated Aug 3, 2024

Denial of service in t2bot.io Matrix Media Repo 1.2.6 and earlier allows remote authenticated users to interrupt service via a crafted image. During thumbnailing, the server decodes a compact, complex image into extremely large dimensions and attempts to hold the entire expanded image in memory without an effective bound. An account able to upload media can exhaust server memory and interrupt the repository service, while confidentiality and integrity remain unaffected.

CVSS severity6.5
Medium
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in t2bot.io Matrix Media Repo 1.2.6 and earlier allows remote authenticated users to interrupt service via a crafted image. During thumbnailing, the server decodes a compact, complex image into extremely large dimensions and attempts to hold the entire expanded image in memory without an effective bound. An account able to upload media can exhaust server memory and interrupt the repository service, while confidentiality and integrity remain unaffected.

The record

CVE
CVE-2021-29453
Published
Apr 19, 2021
Updated
Aug 3, 2024
Vendor
t2bot.io
Product
Matrix Media Repo
Classifications
CWE-770, CWE-20, CWE-400, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=<= 1.2.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

t2bot.io · Matrix Media Repoversion=<= 1.2.6

Published CVSS scores

6.5NISTCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0NISTAV:N/AC:L/Au:S/C:N/I:N/A:P
5.7GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

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 exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CWE-20Improper Input Validation
CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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.

Reported exploitation

Technologies

Your stack

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Your stack

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