CVE-2020-21048Network attack vector

Denial of service via paletted PNG handling

Published Sep 14, 2021 · Updated Aug 4, 2024

libsixel before 1.8.4 allows remote attackers to cause a denial of service when a crafted PNG file is decoded by an application. The dither.c sixel_dither_new routine mishandles a one-color paletted PNG palette, permitting an illegal memory access during palette setup. Exploitation requires an application to process the attacker-supplied image; the demonstrated consequence is service interruption without reported confidentiality or integrity impact.

CVSS severity6.5
Medium
EPSS probability1.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

libsixel before 1.8.4 allows remote attackers to cause a denial of service when a crafted PNG file is decoded by an application. The dither.c sixel_dither_new routine mishandles a one-color paletted PNG palette, permitting an illegal memory access during palette setup. Exploitation requires an application to process the attacker-supplied image; the demonstrated consequence is service interruption without reported confidentiality or integrity impact.

The record

CVE
CVE-2020-21048
Published
Sep 14, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499.002
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

4.3NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/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.

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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

T1499.002Service Exhaustion

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.

Technologies

Your stack

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Your stack

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