CVE-2021-40633Public exploitNetwork attack vector

Service interruption via unbounded screen allocation

Published Jun 14, 2022 · Updated Aug 4, 2024

Memory exhaustion in gif2rgb in GIFLIB 5.1.4 allows remote attackers to interrupt service by supplying a crafted GIF file. The GIF2RGB routine trusts attacker-controlled logical-screen dimensions and allocates a full screen buffer before validating later records, so a 32-byte image declaring 65,503 by 65,503 pixels consumes about 4 GiB. Processing the file with the command-line utility is required; the upstream issue reports system-wide memory exhaustion and process termination, not confidentiality or integrity loss.

CVSS severity8.8
High
EPSS probability1.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory exhaustion in gif2rgb in GIFLIB 5.1.4 allows remote attackers to interrupt service by supplying a crafted GIF file. The GIF2RGB routine trusts attacker-controlled logical-screen dimensions and allocates a full screen buffer before validating later records, so a 32-byte image declaring 65,503 by 65,503 pixels consumes about 4 GiB. Processing the file with the command-line utility is required; the upstream issue reports system-wide memory exhaustion and process termination, not confidentiality or integrity loss.

The record

CVE
CVE-2021-40633
Published
Jun 14, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 14, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

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

5.1NIST NVDAV:N/AC:H/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

Public exploit references

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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