CVE-2020-21677

Name: CVE-2020-21677
Creator: NVD / NIST
Published: 2021-08-10T21:15:07.447+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.90%

Last modified Jun 17, 2026

CVE-2020-21677 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.. EPSS estimates a 0.90% chance of exploitation in the next 30 days.

Description

A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS Probability

0.90%

55.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Saitoha	Libsixel	1.8.4

References

https://github.com/saitoha/libsixel/issues/123Exploit, Issue Tracking, Patch, Third Party Advisory
https://github.com/saitoha/libsixel/issues/123Exploit, Issue Tracking, Patch, Third Party Advisory

Timeline

Published: Aug 10, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-21677?

How severe is CVE-2020-21677?

CVE-2020-21677 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.90% probability of exploitation in the next 30 days.

How do I fix CVE-2020-21677?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-21677?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST