CVE-2021-27923Network attack vector

Service interruption via unchecked ICO frame dimensions

Published Mar 3, 2021 · Updated Aug 15, 2025

Uncontrolled resource consumption in Pillow before 8.1.2 allows attackers to interrupt service by supplying a crafted ICO image. IcoImagePlugin.frame() constructs a PngImageFile directly and trusts its embedded dimensions without the decompression-bomb check normally applied by Image.open(). Exploitation requires an application to process an attacker-controlled ICO containing a PNG frame, which can exhaust process memory until the application cannot continue processing.

CVSS severity8.7
High
EPSS probability3.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Pillow before 8.1.2 allows attackers to interrupt service by supplying a crafted ICO image. IcoImagePlugin.frame() constructs a PngImageFile directly and trusts its embedded dimensions without the decompression-bomb check normally applied by Image.open(). Exploitation requires an application to process an attacker-controlled ICO containing a PNG frame, which can exhaust process memory until the application cannot continue processing.

The record

CVE
CVE-2021-27923
Published
Mar 3, 2021
Updated
Aug 15, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.7GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-20Improper Input Validation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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