CVE-2020-21050Public exploitNetwork attack vector

Process crash via unchecked GIF LZW code size

Published Sep 14, 2021 · Updated Aug 4, 2024

Stack buffer overflow in Libsixel before 1.8.3 allows context-dependent attackers to crash GIF-consuming processes via a crafted GIF. The gif_process_raster function accepts an LZW minimum code size above 12, derives indices from it, and writes outside its fixed 4,096-entry codes table. Processing attacker-supplied GIF content is required, and successful exploitation interrupts the consuming process by causing a crash.

CVSS severity6.5
Medium
EPSS probability1.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in Libsixel before 1.8.3 allows context-dependent attackers to crash GIF-consuming processes via a crafted GIF. The gif_process_raster function accepts an LZW minimum code size above 12, derives indices from it, and writes outside its fixed 4,096-entry codes table. Processing attacker-supplied GIF content is required, and successful exploitation interrupts the consuming process by causing a crash.

The record

CVE
CVE-2020-21050
Published
Sep 14, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 14, 2021CVE 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

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P

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 exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

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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